U.S. patent number 7,117,738 [Application Number 10/952,852] was granted by the patent office on 2006-10-10 for liquid level detecting apparatus.
This patent grant is currently assigned to Denso Corporation. Invention is credited to Isao Miyagawa, Atsushi Yasuda.
United States Patent |
7,117,738 |
Miyagawa , et al. |
October 10, 2006 |
Liquid level detecting apparatus
Abstract
A guide pipe is formed from a metal material, and its internal
cross section has a circular shape whose diametric dimension
gradually becomes smaller with a distance from an ultrasonic
sensor. That is, the guide pipe is formed so that a route for
transmitting an ultrasonic wave generated from the ultrasonic
sensor may be tapered from this ultrasonic sensor toward a
reflector plate. Thus, the acoustic pressure level of the
ultrasonic wave which enters the reflector plate can be made higher
than a value in a prior-art liquid level detecting apparatus.
Accordingly, the energy of the ultrasonic wave generated from the
ultrasonic sensor can be utilized for liquid level detection at a
high efficiency, so that a fuel liquid level detecting apparatus
capable of accurate liquid level detection can be provided.
Inventors: |
Miyagawa; Isao (Kariya,
JP), Yasuda; Atsushi (Kariya, JP) |
Assignee: |
Denso Corporation (Kariya,
JP)
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Family
ID: |
35504095 |
Appl.
No.: |
10/952,852 |
Filed: |
September 30, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050284217 A1 |
Dec 29, 2005 |
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Foreign Application Priority Data
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Oct 2, 2003 [JP] |
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2003-344888 |
Oct 24, 2003 [JP] |
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2003-365106 |
Oct 28, 2003 [JP] |
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2003-367904 |
Jan 19, 2004 [JP] |
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2004-010954 |
Jan 19, 2004 [JP] |
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2004-010955 |
Aug 3, 2004 [JP] |
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2004-227003 |
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Current U.S.
Class: |
73/290V; 73/644;
73/642 |
Current CPC
Class: |
G01F
23/2962 (20130101); G01N 2291/02836 (20130101) |
Current International
Class: |
G01F
23/00 (20060101); G01F 23/28 (20060101) |
Field of
Search: |
;73/290V,642,644 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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A-11-153471 |
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Jun 1999 |
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JP |
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A-2001-208595 |
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Aug 2001 |
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JP |
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Primary Examiner: Williams; Hezron
Assistant Examiner: Shah; Samir
Attorney, Agent or Firm: Posz Law Group, PLC
Claims
What is claimed is:
1. A liquid level detecting apparatus comprising: an ultrasonic
sensor installed in a bottom of a tank storing a liquid and
detecting a liquid level of the liquid by generating an ultrasonic
wave and receiving the ultrasonic wave reflected by the liquid
level; a reflector directing the ultrasonic wave to the liquid
level; a first cylinder enclosing a first route transmitting the
ultrasonic wave between the ultrasonic sensor and the reflector and
shaped to have an internal sectional area thereof perpendicular to
the first route, the area gradually decreasing toward the
reflector; and a second cylinder enclosing a second route
transmitting the ultrasonic wave between the reflector and the
liquid level.
2. The liquid level detecting apparatus according to claim 1,
wherein each of the first and the second cylinders has a generally
round cross-sectional shape perpendicular to a longitudinal axis
thereof.
3. The liquid level detecting apparatus according to claim 2,
wherein a diametric dimension of an end of the first cylinder on
the side of the reflector is set to be generally equal to a
diametric dimension of an end of the second cylinder on the side of
the reflector.
4. The liquid level detecting apparatus according to claim 3,
wherein the second cylinder has a generally uniform diametric
dimension over the entire length thereof.
5. The liquid level detecting apparatus according to claim 1,
wherein the first and the second cylinders are made of metallic
material.
6. The liquid level detecting apparatus according to claim 1,
further comprising: a baffle plate whose lower surface is generally
in parallel to and at the height of a maximum level of the liquid
level, wherein at least one of the second cylinder and the baffle
plate comprises a passage communicating one side of the baffle
plate with another side thereof.
7. The liquid level detecting apparatus according to claim 1,
wherein the first cylinder comprises a step therein reflecting the
ultrasonic wave generated by the ultrasonic sensor back to the
ultrasonic sensor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
of: Japanese Patent Application No. 2003-344888 filed on Oct. 2,
2003; Japanese Patent Application No. 2003-365106 filed on Oct. 24,
2003; Japanese Patent Application No. 2003-367904 filed on Oct. 28,
2003; Japanese Patent Application No. 2004-010954 filed on Jan. 19,
2004; Japanese Patent Application No. 2004-010955 filed on Jan. 19,
2004; and Japanese Patent Application No. 2004-227003 filed on Aug.
3, 2004, the contents of which are incorporated herein by
reference.
FIELD OF THE INVENTION
The present invention relates to a liquid level detecting apparatus
for detecting the liquid surface height of a liquid within a tank,
and it is well suited for use in, for example, detecting the liquid
level of a fuel within a fuel tank which is mounted in an
automobile.
BACKGROUND OF THE INVENTION
Heretofore, a liquid level detecting apparatus which detects the
liquid surface level of a liquid within a tank has been, for
example, one comprising an ultrasonic sensor which is installed in
the fuel, and a reflector plate which is installed in the fuel and
which turns an ultrasonic wave from the ultrasonic sensor toward
the liquid level, wherein the ultrasonic wave reflected by the
liquid level is received by the ultrasonic sensor through the
reflector plate so as to calculate the liquid surface level (refer
to, for example, JP11-153471A).
In the liquid level detecting apparatus stated above, a cylinder
having a square internal cross section is fixed to a bottom surface
within the fuel tank. The ultrasonic sensor is attached to one end
side of the cylinder so as to be capable of generating the
ultrasonic wave toward the other end side of the cylinder, while
the reflector plate which turns the ultrasonic wave having
proceeded inside the cylinder, toward the liquid level is disposed
on the other end side of the cylinder. The cylinder forms an
ultrasonic transmission route in the liquid level detecting
apparatus.
In the prior-art liquid level detecting apparatus stated above, the
cylinder is formed having the square internal cross section, and a
uniform cross-sectional shape in the direction of the longitudinal
axis of this cylinder. That is, among four wall surfaces which
constitute the cylinder, two opposing ones are in a relationship in
which they are parallel to each other.
The ultrasonic wave proceeds inside the cylinder while iterating
reflections by the respective wall surfaces of the cylinder.
Herein, each time the ultrasonic wave is reflected by the wall
surface, it undergoes partial transmission through the wall
surface, etc., so that the energy of the ultrasonic wave decreases
gradually.
In the cylinder which is included in the prior-art liquid level
detecting apparatus stated above, that is, in the cylinder whose
cross-sectional shape is uniform in substantially the whole region
thereof in the axial direction, the intensity of the ultrasonic
wave entering the reflector plate, in other words, the acoustic
pressure level of the ultrasonic wave per unit area in the cross
section of the cylinder becomes lower than the acoustic pressure
level of the ultrasonic wave in the vicinity of the ultrasonic
sensor.
Therefore, the acoustic pressure level of the ultrasonic wave which
is turned by the reflector plate toward the liquid level lowers.
Consequently, the acoustic pressure level of the ultrasonic wave
which is reflected by the liquid level lowers. Accordingly, it
becomes difficult to detect the liquid level at a high
accuracy.
Moreover, in a case where the fuel has quaked on account of the
vibration of a vehicle, the travel thereof on a sloping road, or
the like, the liquid level within the fuel tank comes above the
cylinder and becomes slant especially when it is high. On this
occasion, it is sometimes the case that the ultrasonic wave having
proceeded inside the cylinder and arrived at the liquid level is
reflected by this liquid level to proceed outside the cylinder, and
that the reflected ultrasonic wave is not received by the
ultrasonic sensor. Then, the problem occurs that the indicated
value of a fuel indicator becomes unstable.
Further, in consideration of the fact that the velocity of an
ultrasonic wave in a liquid changes depending upon the temperature,
pressure, etc. of the liquid, there has been proposed a
construction wherein an ultrasonic sensor is attached to the
outside surface of the bottom of a liquid container so as to be
capable of generating the ultrasonic wave toward the upper part of
the interior of the container, and an ultrasonic reflector which
turns the ultrasonic wave from the ultrasonic sensor, toward this
ultrasonic sensor is installed at the position of a predetermined
measurement reference height at the lower part of the interior of
the container (refer to, for example, JP2001-208595A).
According to the construction, the ultrasonic sensor detects two
sorts of data, namely, the round-trip time between the ultrasonic
sensor and a liquid level and the round-trip time between the
ultrasonic sensor and the reflector. Since the distance between the
ultrasonic sensor and the reflector is known beforehand, the
velocity of the ultrasonic wave in temperature and pressure
conditions at that point of time can be directly and accurately
calculated from the round-trip time between the ultrasonic sensor
and the reflector. The position of the liquid level can be
accurately detected from the ultrasonic velocity thus obtained, and
the round-trip time between the ultrasonic sensor and the liquid
level.
In the prior-art liquid level detecting apparatus stated above,
however, the reflector is a component separate from the ultrasonic
sensor, and it becomes difficult to keep the positional
relationship of both the constituents highly accurate, because of
the construction in which these constituents are fixed to the
container. The accuracy of the positional relationship between the
ultrasonic generation sensor and the ultrasonic reflector is
greatly relevant to the measurement accuracy of the ultrasonic
velocity in the liquid. Therefore, when the accuracy of the
positional relationship between both the constituents lowers, the
ultrasonic velocity in the liquid cannot be detected at a high
accuracy, making it impossible to accurately detect the liquid
level position.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid level
detecting apparatus which can detect the height of a liquid surface
accurately and stably.
A liquid level detecting apparatus according to the invention is
constructed comprising an ultrasonic sensor, a reflector, a first
cylinder and a second cylinder.
The ultrasonic sensor is installed at the bottom of a tank in which
a liquid is stored, and it detects the position of a liquid level
by generating an ultrasonic wave and receiving the ultrasonic wave
reflected by the liquid level of the liquid.
The reflector turns the ultrasonic wave generated from the
ultrasonic sensor, toward the liquid level.
The first cylinder encloses a first route which transmits the
ultrasonic wave between the ultrasonic sensor and the reflector,
and it is formed so that its internal sectional area in a plane
perpendicular to the first route may gradually become smaller
toward the reflector.
The second cylinder encloses a second route which transmits the
ultrasonic wave between the reflector and the liquid level.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will be
appreciated, as well as methods of operation and the function of
the related parts, from a study of the following detailed
description, appended claims, and drawings, all of which form a
part of this application. In the drawings:
FIG. 1 is a partial sectional view of the first embodiment of a
liquid level detecting apparatus according to the invention;
FIG. 2 is a sectional view taken along plane II--II in FIG. 1;
FIG. 3 is a schematic diagram showing an electric circuit
arrangement in the first embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 4 is a view seen along arrow IV in FIG. 1;
FIG. 5 is a partial sectional view of the second embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 6 is a view seen along arrow VI in FIG. 5;
FIG. 7 is a schematic diagram showing an electric circuit
arrangement in the second embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 8 is a plan view showing a modification of a baffle plate in
the second embodiment of the liquid level detecting apparatus
according to the invention;
FIG. 9 is a plan view showing another modification of the baffle
plate in the second embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 10 is a partial sectional view of the third embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 11 is a view seen along arrow XI in FIG. 10;
FIG. 12 is a schematic diagram showing an electric circuit
arrangement in the third embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 13 is a partial sectional view of a modification to the third
embodiment of the liquid level detecting apparatus according to the
invention;
FIG. 14 is a partial sectional view of the fourth embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 15 is a schematic diagram showing an electric circuit
arrangement in the fourth embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 16 is a flow chart showing a process based on a control
circuit, in the fourth embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 17 is a flow chart showing a process based on a control
circuit, in the fifth embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 18 is a partial sectional view of the sixth embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 19 is a partial sectional view of the seventh embodiment of
the liquid level detecting apparatus according to the
invention;
FIG. 20 is a schematic diagram showing an electric circuit
arrangement in the seventh embodiment of the liquid level detecting
apparatus according to the invention;
FIG. 21 is a partial sectional view of the eighth embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 22 is a view seen along arrow XXII in FIG. 21;
FIG. 23 is a partial sectional view of the ninth embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 24 is a partial sectional view of the tenth embodiment of the
liquid level detecting apparatus according to the invention;
FIG. 25 is a partial sectional view of a modification to the
seventh embodiment of the liquid level detecting apparatus
according to the invention;
FIG. 26 is a partial sectional view of the eleventh embodiment of
the liquid level detecting apparatus according to the
invention;
FIG. 27 is an enlarged sectional view of part XXVII in FIG. 26;
FIG. 28 is a schematic diagram showing an electric circuit
arrangement in the eleventh embodiment of the liquid level
detecting apparatus according to the invention;
FIG. 29 is a partial sectional view of a modification to the
eleventh embodiment of the liquid level detecting apparatus
according to the invention; and
FIG. 30 is a partial sectional view of another modification to the
eleventh embodiment of the liquid level detecting apparatus
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In each of the ensuing embodiments, the present invention will be
described as a fuel liquid level detecting apparatus for detecting
a fuel liquid level position in the fuel tank of an automobile.
(First Embodiment)
As shown in FIG. 1, a fuel liquid level detecting apparatus 1A
includes a fuel tank 2, an ultrasonic sensor 3, a guide pipe (first
cylinder) 4, a reflector plate 6, and a guide pipe (second
cylinder) 5. Herein, the ultrasonic sensor 3, guide pipe 4,
reflector plate 6 and guide pipe 5 are unitarily accommodated and
held in a body 7, and they are attached to the bottom surface 21 of
the fuel tank 2 through the body 7 as shown in FIG. 1.
The ultrasonic sensor 3 is installed on one end side of the guide
pipe 4 in a state where the ultrasonic generation surface 31
thereof for generating an ultrasonic wave opposes to the interior
of the guide pipe 4. That is, the ultrasonic sensor 3 is fixed to a
bracket 15, and the bracket 15 is fitted in the body 7.
The ultrasonic sensor 3 is formed from a substance having a
piezoelectric effect, for example, PZT (lead titanate zirconate).
The ultrasonic sensor 3 has lead wires 14 for connection to an
external electric circuit. The lead wires 14 are extended out of
the bracket 15, and are further led out of the fuel tank 2
hermetically. Here, the "piezoelectric effect" signifies the
property that a volume is changed when a voltage is applied, while
a voltage is generated when a force is received from outside.
The ultrasonic generation surface 31 of the ultrasonic sensor 3 is
formed to be circular. When a pulse-shaped voltage is impressed on
the ultrasonic sensor 3 through the lead wires 14, the ultrasonic
generation surface 31 vibrates, whereby the ultrasonic wave is
generated from the ultrasonic generation surface 31 into a fuel 8.
On the other hand, when a reflected wave with the ultrasonic wave
reflected by the liquid level of the fuel 8 arrives at the
ultrasonic generation surface 31 to vibrate this ultrasonic
generation surface 31 under the pressure action of the reflected
wave, the ultrasonic sensor 3 generates a voltage, which is
externally delivered as an output signal through the lead wires
14.
The bracket 15 is formed substantially in the shape of a bottomed
cylinder from a resin or a metal, and the ultrasonic sensor 3 is
fixed on the bottom 15b of the bracket 15 by, for example, bonding.
A plug 13 is fixed on the open end side (right side in FIG. 1) of
the bracket 15 by bonding, pressed fitting or the like. The plug 13
has the lead wires 14 inserted therethrough so as to hold them, and
also prevents foreign matters from intruding into the bracket
15.
The bracket 15 is fixed on one end side (right side in FIG. 1) of
the guide pipe 4 so that the ultrasonic generation surface 31 of
the ultrasonic sensor 3 may face the other end (left side in FIG.
1) of the guide pipe 4, in other words, that the ultrasonic wave
generated by the ultrasonic sensor 3 may be transmitted toward the
other end side (left side in FIG. 1) within the guide pipe 4.
When the pulse-shaped voltage is impressed the ultrasonic sensor 3
through the lead wires 14, the ultrasonic generation surface 31
vibrates, and the vibration of the ultrasonic generation surface 31
is conveyed to the bottom 15b of the bracket 15. Further, the
ultrasonic wave is generated from the outside surface 15a of the
bracket 15 into the fuel 8. On the other hand, the ultrasonic wave
is reflected by the liquid level 81 of the fuel 8 or the step 41 of
the guide pipe 4, the reflected wave arrives at the ultrasonic
generation surface 31 through the front surface 15a of the bracket
15, and the ultrasonic generation surface 31 vibrates under the
pressure action of the reflected wave. Then, the ultrasonic sensor
3 generates the voltage, which is externally delivered as the
output signal through the lead wires 14.
The guide pipe 4 which encloses the ultrasonic transmission route
(first route) A between the ultrasonic sensor 3 and the reflector
plate 6 is formed from an alloy for aluminum die casting, and one
end side (right side in FIG. 1) of this guide pipe 4 is held in
touch with the bracket 15 to which the ultrasonic sensor 3 is
fixed.
As shown in FIG. 2, the guide pipe 4 is formed so that a circular
internal sectional shape may be defined in a direction
perpendicular to the longitudinal axis A of this guide pipe 4, and
that the internal sectional area of this guide pipe 4 in the
direction perpendicular to the longitudinal axis A may gradually
become smaller toward the reflector plate 6 (leftward in FIG. 1).
More specifically, the guide pipe 4 has an internal diametric
dimension d1 at its end near to the ultrasonic sensor 3 (right side
in FIG. 1), while it has an internal diametric dimension d2 at its
end near to the reflector plate 6 (left side in FIG. 1) (here,
d1>d2 holds).
The guide pipe 4 and the body 7 are respectively formed with
through holes 4a and 7a, which communicate with each other. The
fuel 8 flows into the guide pipe 4 through the through holes 4a and
7a.
Besides, the guide pipe 4 is formed with the correcting reflective
surface (step) 41. As shown in FIG. 2, the correcting reflective
surface 41 is formed in the shape of a ring and as a surface
opposing to the ultrasonic sensor 3. Accordingly, part of the
ultrasonic wave generated from the ultrasonic sensor 3 enters the
correcting reflective surface 41. The partial ultrasonic wave is
reflected by the correcting reflective surface 41, and is received
by the ultrasonic sensor 3.
Besides, the reflector plate 6 which turns the ultrasonic wave
generated from the ultrasonic sensor 3, toward the liquid level 81
within the fuel tank 2, is installed on the side of the guide pipe
4 remote from the ultrasonic sensor 3 (left side in FIG. 1). The
reflector plate 6 is formed of a stainless steel plate.
The reflector plate 6 turns the ultrasonic wave generated from the
ultrasonic sensor 3 as has fallen on the reflective surface 61 of
this reflector plate 6, toward the liquid level 81. More
specifically, the reflector plate 6 is installed so as to turn the
ultrasonic wave proceeding along the longitudinal axis A of the
guide pipe 4, into a direction in which an incident angle on the
liquid level 81 becomes zero degree, that is, into a direction
which is perpendicular to the liquid level 81. In other words, the
reflective surface 61 is located in a state where it is inclined 45
degrees relative to the liquid level 81.
The guide pipe 5 which encloses the ultrasonic transmission route
(second route) B between the reflector plate 6 and the liquid level
81, is formed of a stainless steel tube. The sectional shape of the
guide pipe 5 in a direction perpendicular to the longitudinal axis
B thereof is formed to be circular, while the diameter of this
guide pipe 5 has a diametric dimension d3 uniformly over the full
length thereof. The diametric dimension d3 of the guide pipe 5 is
made equal to the diametric dimension d2 of the guide pipe 4 at the
end thereof on the side of the reflector plate 6.
A dashboard 51 is installed at the distal end of the guide pipe 5
remote from the reflector plate 6. When an automobile jolts during
its travel on a bad road by way of example, the liquid level 81
within the fuel tank 2 consequently quakes to wave. On this
occasion, when the wave flows into the guide pipe 5 through the
opening of this guide pipe 5 on the upper end side thereof, the
liquid level 81 temporarily rises, and hence, the accurate
detection of the liquid level 81 becomes difficult. Therefore, the
dashboard 51 as shown in FIG. 1 is installed at the distal end of
the guide pipe 5. Thus, even when the automobile has jolted to give
rise to the wave in the fuel tank 2, the flow of the fuel 8 into
the guide pipe 5 can be prevented, and hence, the accurate
detection of the liquid level 81 is permitted.
The dashboard 51 is provided with notches 52 as shown in FIG. 4,
whereby the air is permitted to communicate inside and outside the
guide pipe 5. Accordingly, even when the dashboard 51 is installed,
the liquid level 81 inside the guide pipe 5 can satisfactorily
follow up the fluctuation of the liquid level 81 outside the guide
pipe 5. Besides, as shown in FIG. 1, the distal end position of the
guide pipe 5 on the side of the liquid level 81 is set so as to
protrude a predetermined length above the liquid level 82 of the
fuel 8 in the case where the storage quantity of the fuel 8 in the
fuel tank 2 is the maximum, in other words, where the fuel tank 2
is full.
The bracket 15 for fixing the ultrasonic sensor 3 thereto, the
guide pipe 4, the reflector plate 6 and the guide pipe 5 as
described above, are installed on the body 7. The body 7 is formed
from a resin material, for example, a resin material which exhibits
an excellent stability against the fuel 8 in the fuel tank 2. The
body 7 fulfills the functions of fixing the above constituent
components while keeping their positional relationships highly
accurate, and fixing the above constituent components on the bottom
surface 21 of the fuel tank 2. Besides, the guide pipe 4, reflector
plate 6 and guide pipe 5 in the state where they are fixed to the
body 7 form a positional relationship in which the longitudinal
axis A of the guide pipe 4 and that B of the guide pipe 5 intersect
with each other on the reflective surface 61 of the reflector plate
6. Concretely, the bracket 15 for fixing the ultrasonic sensor 3
thereto, the guide pipe 4, the reflector plate 6 and the guide pipe
5 are assembled to the body 7.
As shown in the block diagram of electric circuitry in FIG. 3, a
control circuit 100 is connected to a battery 112 through an
ignition switch 111. Besides, the control circuit 100 has the
ultrasonic sensor 3 connected thereto. Also, the control circuit
100 has a display unit 110 connected thereto.
The control circuit 100 is constructed of, for example, a
microcomputer, and it includes a pulse generation circuit 101 which
applies a pulse-shaped voltage to the ultrasonic sensor 3, an
arithmetic circuit 102 which processes a reflected-wave reception
signal outputted from the ultrasonic sensor 3 and which calculates
the position of the liquid level 81 on the basis of the reception
signal, and a drive circuit 103 which outputs a drive signal for
driving the display unit 110, on the basis of a liquid-level
position signal calculated by the arithmetic circuit 102. When the
control circuit 100 is fed with electric power from the battery 112
by the closure of the ignition switch 111, the fuel liquid level
detecting apparatus 1A starts its operation.
The display unit 110 is constructed of, for example, a needle
instrument or a liquid crystal panel, and it is installed in a
combination meter (not shown) located in front of the driver seat
of the automobile. The display unit 110 is driven by the drive
circuit 103 of the control circuit 100, and it displays the
position of the liquid level 81 calculated by the arithmetic
circuit 102, in other words, the reserve or remaining quantity of
the fuel 8 within the fuel tank 2 so as to be visually recognizable
by the driver of the automobile.
Next, the operation of detecting the fuel liquid level by the fuel
liquid level detecting apparatus 1A will be described.
When impressed with the pulse-shaped voltage signal by the pulse
generation circuit 101, the ultrasonic sensor 3 generates a
pulse-shaped ultrasonic wave into the fuel 8 within the fuel tank
2. Then, the ultrasonic generation surface 31 of the ultrasonic
sensor 3 vibrates, the vibration of the ultrasonic generation
surface 31 is conveyed to the bottom 15b of the bracket 15, and an
ultrasonic wave is further generated from the outside surface 15a
of the bracket 15 into the fuel 8. Part of this ultrasonic wave
proceeds inside the guide pipe 4, and enters the correcting
reflective surface 41. The partial ultrasonic wave is reflected by
the correcting reflective surface 41, and it enters the ultrasonic
generation surface 31 of the ultrasonic sensor 3 again. On the
other hand, part of the pulse-shaped ultrasonic wave generated from
the ultrasonic sensor 3 into the fuel 8 proceeds inside the guide
pipe 4 and enters the reflective surface 61. The partial ultrasonic
wave is reflected by the reflective surface 61, and it proceeds
inside the guide pipe 5 and toward the liquid level 81. Further, it
is reflected by the liquid level. 81, and it enters the ultrasonic
sensor 3 along the same route as that of the going path, that is,
via the guide pipe 5, reflective surface 61 and guide pipe 4.
Thus, when the ultrasonic sensor 3 is driven by the pulse
generation circuit 101 to generate the single ultrasonic pulse, it
receives the two reflected pulses; the reflected pulse from the
correcting reflective surface 41 and the reflected pulse from the
liquid level 81, in correspondence with the single-pulse generation
as described above. As seen from FIG. 1, a transmission route
length from the ultrasonic sensor 3 to the correcting reflective
surface 41 is less than a transmission route length from the
ultrasonic sensor 3 to the liquid level 81. Therefore, the
ultrasonic sensor 3 first receives the reflected pulse from the
correcting reflective surface 41 and subsequently receives the
reflected pulse from the liquid level 81. When the ultrasonic
sensor 3 receives the respective reflected pulses, it generates
voltage signals, which are inputted to the arithmetic circuit
102.
The arithmetic circuit 102 calculates time periods which are
expended since the issue of the pulse-shaped voltage signal by the
pulse generation circuit 101, till the detections of the two
reflected pulses stated above, respectively.
Here, the correcting reflective surface 41 is provided at a
predetermined position relative to the ultrasonic sensor 3. That
is, the distance between the correcting reflective surface 41 and
the ultrasonic sensor 3 is known. Accordingly, the arithmetic
circuit 102 calculates the propagation velocity of the ultrasonic
pulse in the fuel 8, on the basis of the time period since the
issue of the pulse-shaped voltage signal by the pulse generation
circuit 101 till the reception of the reflected pulse from the
correcting reflective surface 41, and the distance between the
correcting reflective surface 41 and the ultrasonic sensor 3.
Subsequently, the arithmetic circuit 102 calculates the position of
the liquid level 81, namely, the height H of the liquid level 81 in
FIG. 1, on the basis of the propagation velocity of the ultrasonic
pulse in the fuel 8 as thus calculated, and the time period since
the issue of the pulse-shaped voltage signal by the pulse
generation circuit 101 till the reception of the reflected pulse
from the liquid level 81. Further, the arithmetic circuit 102
calculates the reserve of the fuel 8 within the fuel tank 2, on the
basis of the prestored shape of the fuel tank 2.
The drive circuit 103 outputs a signal for causing the display unit
110 to display the height H of the liquid level 81 or the reserve
of the fuel 8 as calculated by the arithmetic circuit 102, for
example, a drive signal for turning a needle shaft (not shown) up
to an angle which corresponds to the height H of the liquid level
81 or the reserve of the fuel 8. Thus, the height H of the liquid
level 81 in the fuel tank 2 or the reserve of the fuel 8 is
displayed by the display unit 110.
Next, there will be described the construction and functional
effects of the guide pipe 4 as form the characterizing features of
the fuel liquid level detecting apparatus 1A.
In the fuel liquid level detecting apparatus 1A, the guide pipe 4
is formed from a metal material, namely, an aluminum die casting
material. The internal section of the guide pipe 4 in a direction
perpendicular to the longitudinal axis A thereof, that is, the
internal cross-sectional shape is made circular, and the diametric
dimension of the internal cross section of this guide pipe 4 is
made smaller with a distance from the ultrasonic sensor 3. In other
words, the guide pipe 4 is formed so that the ultrasonic
transmission route may taper from the ultrasonic sensor 3 toward
the reflector plate 6.
Thus, the degree of attenuation of ultrasonic energy as is involved
while the ultrasonic wave generated from the ultrasonic sensor 3
proceeds to the reflector plate 6 inside the guide pipe 4 can be
made lower than in case of the prior-art liquid level detecting
apparatus, whereby the acoustic pressure level of the ultrasonic
wave in the vicinity of the end of the guide pipe 4 on the side of
the reflector plate 6, namely, the acoustic pressure level of the
ultrasonic wave falling on the reflector plate 6 can be made higher
than a level in the prior-art liquid level detecting apparatus.
Accordingly, the energy of the ultrasonic wave generated from the
ultrasonic sensor 3 can be utilized for the liquid level detection
at a high efficiency, so that the fuel liquid level detecting
apparatus 1A capable of the liquid level detection at a high
accuracy can be provided.
Besides, in the fuel liquid level detecting apparatus 1A, the
diametric dimension d2 of the end of the guide pipe 4 on the side
of the reflector plate 6 is set to be equal to the diametric
dimension d3 of the end of the guide pipe 5 on the side of the
reflector plate 6.
On this occasion, in a case where the ultrasonic wave generated
from the ultrasonic sensor 3 is transmitted from the guide pipe 4
into the guide pipe 5 via the reflector plate 6, and in a case
where the ultrasonic wave reflected by the liquid level 81 is
transmitted from the guide pipe 5 into the guide pipe 4 via the
reflector plate 6, the cross-sectional areas of the transmission
routes hardly change at the transitional part between the guide
pipes 4 and 5. Accordingly, the energy losses of the ultrasonic
waves are difficult to occur at the joint part between the guide
pipes 4 and 5.
Besides, in the fuel liquid level detecting apparatus 1A, the guide
pipe 5 is formed so as to have the uniform diametric dimension over
the full length thereof.
Thus, the guide pipe 5 can be formed of, for example, a steel pipe
being easily available, so that the cost of the fuel liquid level
detecting apparatus 1A can be lowered. Besides, when the shape of
the fuel tank 2 is altered in correspondence with the vehicle for
mounting this fuel tank thereon, the height of the liquid level 82
of the fuel tank 2 in a full tank condition changes, and hence, the
length of the guide pipe 5 needs to be changed correspondingly. In
this case, with the construction in which the guide pipe 5 is
formed of the steel pipe, the fuel liquid level detecting apparatus
1A corresponding to the fuel tank 2 of the different shape can be
fabricated by the very simple expedient of altering the length of
the guide pipe 5.
Besides, in the fuel liquid level detecting apparatus 1A, the guide
pipes 4 and 5 are respectively formed from the metal materials.
The metal materials exhibit high reflection factors for the
ultrasonic waves, in other words, they are difficult to transmit
the ultrasonic waves therethrough. Therefore, when the guide pipes
4 and 5 are formed from the metal materials, the energy losses of
the ultrasonic waves in the courses in which the ultrasonic waves
proceed inside the guide pipes 4 and 5 are suppressed to the
minima, whereby the energy of the ultrasonic wave generated from
the ultrasonic sensor 3 can be utilized for the liquid level
detection at a high efficiency.
By the way, in the fuel liquid level detecting apparatus 1A, the
guide pipe 4 is formed from the aluminum die casting alloy, while
the guide pipe 5 is formed of the stainless steel pipe. However,
the guide pipes 4 and 5 need not be restricted to these metal
materials, but other kinds of metal materials may well be employed.
By way of example, it is also allowed to form the guide pipe 4 from
a steel material, and to form the guide pipe 5 out of an aluminum
pipe. Further, the guide pipes 4 and 5 may well be formed from
substances other than the metal materials, for example, resin
materials or ceramics materials. Any materials may be used as long
as they can efficiently transmit the ultrasonic waves.
Besides, the fuel liquid level detecting apparatus 1A is
constructed in such a manner that the bracket 15 with the
ultrasonic sensor 3 fixed thereto, the guide pipe 4, the reflector
plate 6 and the guide pipe 5 are assembled to the body 7. However,
the detecting apparatus 1A need not be restricted to such a
construction, but it may well be constructed, for example, in such
a way that, at the resin molding of the body 7, the guide pipe 4,
reflector plate 6 and guide pipe 5 are simultaneously formed by
insert molding, whereupon the bracket 15 with the ultrasonic sensor
3 fixed thereto is assembled to the body 7.
Besides, the fuel liquid level detecting apparatus 1A is
constructed in such a manner that the guide pipe 4, guide pipe 5
and reflector plate 6 are formed as the components independent of
one another, and that they are assembled to the body 7. However, at
least two of the guide pipe 4, guide pipe 5 and reflector plate 6
may well be unitarily formed as a single component. In this case,
it is also allowed to omit the body 7, and to fix the unitary
component to the fuel tank 2 through the remaining one of the guide
pipe 4, guide pipe 5 and reflector plate 6.
Besides, although the guide pipe 4 is provided with the correcting
reflective surface 41 in the fuel liquid level detecting apparatus
1A, the correcting reflective surface 41 need not be especially
formed. In this case, by way of example, the temperature of the
fuel 8 within the fuel tank 2 is detected by a temperature sensor
(not shown) or the like, and the height H of the liquid level 81 is
calculated by correcting the ultrasonic propagation velocity in the
fuel 8 on the basis of the detected temperature, whereby the height
H of the liquid level 81 can be calculated at a high accuracy.
(Second Embodiment)
As shown in FIG. 5, a fuel liquid level detecting apparatus 1B in a
second embodiment is such that the guide pipe (first cylinder) 4 of
the fuel liquid level detecting apparatus 1A in the first
embodiment is altered into a shape to be stated later, and that a
baffle plate 9 is installed in the guide pipe (second cylinder) 5
instead of the dashboard 51. Besides, the bracket 15 of the fuel
liquid level detecting apparatus 1B is such that the bracket 15 and
the plug 13 fitted therein in the fuel liquid level detecting
apparatus 1A of the first embodiment, are unitarily formed. The
other constituents of the fuel liquid level detecting apparatus 1B
are constructed similarly to the corresponding constituents of the
fuel liquid level detecting apparatus 1A, respectively.
The guide pipe 4 is formed in the shape of a cylinder of uniform
sectional shape from an aluminum die casting alloy. An ultrasonic
sensor 3 is attached to one end side of the guide pipe 4 (right
side in FIG. 5) through the bracket 15. The ultrasonic sensor 3 and
the guide pipe 4 are coaxially installed.
A reflector plate (reflector) 45 is formed unitarily with the guide
pipe 4 on the other end side of the guide pipe 4 (left side in FIG.
5).
The guide pipe 5 is formed in a cylindrical shape, and is fixed on
the side of the guide pipe 4 near to the reflector plate 45. This
guide pipe 5 is formed of a stainless steel pipe, and it is fixed
to the part of the guide pipe 4 corresponding to the reflector
plate 45, by pressed fitting or the like. The full length dimension
L of the guide pipe 5 is set so that the upper end 50 of this guide
pipe 5 near to a liquid level 81 may protrude above the highest
liquid level 81 in the case where a fuel 8 is stored in a fuel tank
2 in the maximum storage quantity, namely, where the fuel tank 2 is
full, and that a clearance .DELTA.L may be defined between the
upper end 50 and the ceiling inside surface 22 of the fuel tank
2.
The baffle plate 9 being a partition plate is attached within the
guide pipe 5. This baffle plate 9 is formed from a metal material
such as aluminum plate, by press work or the like. As shown in FIG.
6, the baffle plate 9 is such that three protuberances 91 are
provided at intervals of 120 degrees on the outer periphery of a
small disc whose diameter is smaller than the inside diameter of
the guide pipe 5.
The diameter of the circumscribed circle of the three protuberances
91 of the baffle plate 9 is set to be slightly larger than the
inside diameter of the guide pipe 5. Accordingly, when the baffle
plate 9 is pressedly fitted from the side of the upper end 50 into
the guide pipe 5, this guide pipe 5 and the protuberances 91 are
elastically deformed, and their restoring forces fix the baffle
plate 9 rigidly inside the guide pipe 5. When the baffle plate 9
has been fixed inside the guide pipe 5, gaps G in the shape of
circular arcs, in other words, passages communicating the front
side and back side of the baffle plate 9, are defined between the
guide pipe 5 and the baffle plate 9 as shown in FIG. 6. Since the
front side and back side of the baffle plate 9 are communicated by
the gaps G, the liquid level 81 inside the guide pipe 5 changes in
interlocking with the fluctuation of the liquid level 81 outside
the guide pipe 5. Accordingly, the position of the liquid level 81
within the fuel tank 2 can be accurately detected by the fuel
liquid level detecting apparatus 1B.
The baffle plate 9 is fixed inside the guide pipe 5 in such a
manner that a liquid level 82 in the case where a fuel storage
quantity within the fuel tank 2 corresponds to 90% of the maximum
storage quantity coincides with the lower surface 92 of the baffle
plate 9, and that the lower surface 92 is parallel to the liquid
level 81. The baffle plate 9 covers a region including the center
of the guide pipe 5, in a state where it is fixed inside the guide
pipe 5.
The operations of detecting the fuel liquid level by the fuel
liquid level detecting apparatus 1B will be described chiefly on
the functional effects of the baffle plate 9 installed in the guide
pipe 5.
(1) Case where the fuel liquid level 81 within the fuel tank 2 lies
between the liquid level 81 corresponding to the full tank
condition and the liquid level 82 corresponding to the 90%-storage
quantity, that is, where the fuel liquid level 81 lies above the
lower surface 92 of the baffle plate 9:
In this case, an ultrasonic pulse generated from the ultrasonic
sensor 3 reaches the lower surface 92 of the baffle plate 9 before
reaching the liquid level 81, it is reflected by the lower surface
92, and the reflected ultrasonic pulse reaches the ultrasonic
sensor 3 again via a transmission route B, a reflective surface 44
and a transmission route A, thereby to vibrate the ultrasonic
generation surface 31 of the ultrasonic sensor 3. Thus, the
ultrasonic sensor 3 generates a voltage signal, and the voltage
signal, namely, a reflected-pulse detection signal is inputted to
an arithmetic circuit 102.
More specifically, in the case where the position of the fuel
liquid level 81 lies between the liquid level 81 corresponding to
the full tank condition and the liquid level 82 corresponding to
the 90%-storage quantity, a time period which is expended since the
issue of a pulse-shaped voltage signal by a pulse generation
circuit 101 till the detection of the voltage signal based on the
reflected pulse, always becomes a constant value. On this occasion,
a liquid level height which is calculated by the arithmetic circuit
102 is the height HB of the baffle plate 9. Accordingly, a fuel
reserve which is indicated on a display unit 110 is always the
maximum quantity.
Here, when the fuel 8 within the fuel tank 2 has quaked due to the
jolting of an automobile during the travel thereof, it is sometimes
the case that the liquid level 81 comes above the upper end 50 of
the guide pipe 5, and that it inclines relative to a horizontal
direction.
In the absence of the baffle plate 9, when the ultrasonic wave
which proceeds from the reflective surface 44 toward the liquid
level 81 by tracing the transmission route B is reflected by the
liquid level 81, the reflected wave proceeds outside the guide pipe
5 without passing through the transmission route B. That is, the
reflected wave from the liquid level 81 is not received by the
ultrasonic sensor 3. Therefore, the arithmetic circuit 102 fails to
accurately calculate the fuel reserve, and a fuel reserve display
by the display unit 110 becomes unstable. As a concrete example, in
a case where the display unit 110 is a needle instrument, there
occurs the drawback that a needle turns unsteadily between a full
tank (F) indication and an empty (E) indication.
In contrast, according to the fuel liquid level detecting apparatus
1B, the reflected wave from the baffle plate 9 is received by the
ultrasonic sensor 3 without fail, and hence, the fuel reserve which
is indicated on the display unit 110 is stable at the maximum
quantity.
Thus, it is possible to obtain the fuel liquid level detecting
apparatus 1B in which, when the liquid level 81 within the fuel
tank 2 has inclined, the indicated value of the display unit 110
can be kept stable, thereby to afford an excellent visuality.
(2) Case where the position of the fuel liquid level 81 within the
fuel tank 2 lies below the liquid level 82 corresponding to the
90%-storage quantity, that is, where it lies below the lower
surface 92 of the baffle plate 9:
In this case, the ultrasonic pulse reaches the liquid level 81
before reaching the lower surface 92 of the baffle plate 9, it is
reflected by the liquid level 81, and the reflected ultrasonic
pulse reaches the ultrasonic sensor 3 again via the transmission
route B, reflective surface 44 and transmission route A, thereby to
vibrate the ultrasonic generation surface 31. Thus, the ultrasonic
sensor 3 generates a voltage signal, and the voltage signal,
namely, a reflected-pulse detection signal is inputted to the
arithmetic circuit 102.
More specifically, in the case where the fuel liquid level 81 lies
below the liquid level 82 corresponding to the 90%-storage
quantity, a time period which is expended since the issue of the
pulse-shaped voltage signal by the pulse generation circuit 101
till the detection of the voltage signal based on the reflected
pulse, changes in correspondence with the position of the liquid
level 81. On this occasion, the arithmetic circuit 102 calculates
an actual liquid level height H. Further, it calculates a fuel
reserve within the fuel tank 2, from the liquid level height H and
a tank shape prestored as data. Besides, the fuel reserve is
indicated on the display unit 110.
Here, when the fuel 8 within the fuel tank 2 has quaked due to the
jolting of the automobile during the travel thereof, it is
sometimes the case that the liquid level 81 comes above the upper
end 50 of the guide pipe 5, and that it inclines relative to the
horizontal direction.
In the absence of the baffle plate 9, when the ultrasonic wave
which proceeds from the reflective surface 44 toward the liquid
level 81 by tracing the transmission route B is reflected by the
liquid level 81, the reflected wave proceeds outside the guide pipe
5 without passing through the transmission route B. That is, the
reflected wave from the liquid level 81 is not received by the
ultrasonic sensor 3. Therefore, the arithmetic circuit 102 fails to
accurately calculate the fuel reserve, and the fuel reserve display
by the display unit 110 becomes unstable. By way of example, in the
case where the display unit 110 is the needle instrument, there
occurs the drawback that the needle turns unsteadily between the
full tank (F) indication and the empty (E) indication.
In contrast, according to the fuel liquid level detecting apparatus
1B, the reflected wave from the baffle plate 9 is received by the
ultrasonic sensor 3 without fail, and hence, the display unit 110
stably indicates that the fuel reserve is the maximum quantity. In
other words, although the needle moves from actual indicated
values, it is stabilized at the maximum value. Accordingly, the
driver of the automobile can readily judge that the movement of the
needle is ascribable to the jolting of the automobile during the
travel, so he/she can devote himself/herself to the drive of the
automobile without feeling uneasy.
In general, when the fuel reserve is from the full tank condition
of 100% of the storage capacity of the fuel tank 2, to about 90% of
the storage capacity, the driver need not consider fuel
replenishment or the like. Accordingly, even when the indicated
value of the display unit 110 is fixed at the full tank indication,
there is no problem.
On the other hand, when the fuel reserve has become less than 90%,
the driver needs to determine a fuel replenishment time while
considering the drive plan of the automobile. Accordingly, a high
accuracy is required of that indicated value of the fuel reserve
which is displayed on the display unit 110. The fuel liquid level
detecting apparatus 1B can satisfactorily meet the requirement.
In the fuel liquid level detecting apparatus 1B described above,
the guide pipe 5 is disposed in such a manner that the upper end 50
is extended above the liquid level 81 in the case where the storage
quantity of the fuel 8 within the fuel tank 2 is the maximum
quantity, and that the clearance .DELTA.L is defined between the
upper end 50 and the ceiling inside surface 22 of the fuel tank 2,
and the baffle plate 9 is fixed inside the guide pipe 5 in such a
manner that its lower surface 92 is substantially parallel to the
liquid level 81, and that the lower surface 92 is held near the
maximum liquid level 81, more particularly, in coincidence with the
liquid level 82 in the case where the fuel storage quantity within
the fuel tank 2 is 90% of the maximum storage quantity. Further,
the gaps G which are the passages for communicating the front side
and back side of the baffle plate 9 are formed between the baffle
plate 9 and the guide pipe 5.
Thus, the attitude of the fuel liquid level detecting apparatus 1B
can be easily changed within the fuel tank 2, so that the job of
attaching the fuel liquid level detecting apparatus 1B into the
fuel tank 2 can be performed with ease.
Besides, in the case where the fuel 8 in the fuel tank 2 has quaked
due to the jolting of the automobile during the travel thereof and
where the liquid level 81 has come above the upper end 50 of the
guide pipe 5 and inclined relative to the horizontal direction, the
liquid level detecting apparatus which is not provided with the
baffle plate 9 undergoes the drawback that, since the reflected
wave from the liquid level 81 proceeds outside the guide pipe 5 and
cannot be received by the ultrasonic sensor 3, the arithmetic
circuit 102 fails to accurately calculate the fuel reserve, so the
fuel reserve display by the display unit 110 becomes unstable. In
contrast, according to the fuel liquid level detecting apparatus
1B, the ultrasonic wave from the ultrasonic sensor 3 is reflected
by the baffle plate 9, and the ultrasonic sensor 3 is permitted to
reliably receive the reflected ultrasonic wave, whereby the fuel
reserve display by the display unit 110 can be made the maximum
quantity and be stably presented. Thus, it is possible to realize
the fuel liquid level detecting apparatus 1B of excellent visuality
in which the indicated value of the display unit 110 can be kept
stable when the liquid level 81 within the fuel tank 2 has
inclined.
Besides, in the fuel liquid level detecting apparatus 1B, the guide
pipe 5 is installed to be substantially coaxial with the
transmission route B being a reflection axis, namely, an axis along
which the ultrasonic wave proceeding along the axis of the
ultrasonic sensor 3, that is, the ultrasonic wave tracing the
transmission route A is reflected by the reflective surface 44 so
as to proceed toward the liquid level 81, and the baffle plate 9
covers the region including, at least, the center of the guide pipe
5.
The ultrasonic wave is conically radiated from the ultrasonic
sensor 3, and the energy of the ultrasonic wave becomes the maximum
in the axial direction of the ultrasonic sensor 3, that is, in the
direction perpendicular to the ultrasonic sensor 3. Accordingly,
the ultrasonic wave in the direction of the maximum energy is
reliably reflected by the baffle plate 9, whereby when the liquid
level 81 lies above the baffle plate 9, the energy of the
ultrasonic wave reflected by the baffle plate 9 and entering the
ultrasonic sensor 3 can be kept high to heighten the output signal
level of the ultrasonic sensor 3.
Besides, in the fuel liquid level detecting apparatus 1B, the
baffle plate 9 is formed as the component separate from the guide
pipe 5 and is thereafter attached to the guide pipe 5.
In this manner, the baffle plate 9 and the guide pipe 5 are
constructed as the separate components. Owing to the construction,
in fabricating the fuel liquid level detecting apparatus 1B adapted
to cope with a plurality of fuel tanks 2 which differ in the height
H of the liquid level 81 in the condition of the maximum storage
quantity of the fuel 8, the guide pipe 5 is used in common, and
merely the position of the fixation of the baffle plate 9 to the
guide pipe 5 is changed in correspondence with the respective fuel
tanks 2, whereby a plurality of sorts of fuel liquid level
detecting apparatuses 1B can be easily fabricated with cost rise
suppressed.
(Modification to Second Embodiment)
In the modification of the baffle plate 9 as shown in FIG. 8, the
baffle plate 9 is formed to be square. In this case, it is also
allowed to employ a polygon different from the square, which has
three or more apices.
In the other modification of the baffle plate 9 as shown in FIG. 9,
the baffle plate 9 is in the shape of a circle, the two
circumferential parts of which are cut away.
By the way, in the fuel liquid level detecting apparatus 1B, the
guide pipe 4 is formed from the aluminum die casting alloy, while
the guide pipe 5 is formed of the stainless steel pipe. However,
the guide pipes 4 and 5 need not be restricted to these metal
materials, but they may well be formed in a combination of other
substances. Alternatively, they may well be formed from an
identical substance. Further, the guide pipes 4 and 5 may well be
formed as a unitary component.
Besides, in the fuel liquid level detecting apparatus 1B, the
baffle plate 9 is formed by press work or the like out of an
aluminum plate, but it may well be formed of another metal plate,
for example, a brass or steel plate. Also, it may well be formed
from a resin material.
Besides, in the fuel liquid level detecting apparatus 1B, the
baffle plate 9 and the guide pipe 5 are formed as the separate
members, but they may well be unitarily formed. By way of example,
they may well be unitarily fabricated from the resin material or
the aluminum die casting alloy.
Besides, in the fuel liquid level detecting apparatus 1B, the
reflective surface 44 is shaped in a flat surface, but it may well
be shaped in a concave surface which is concave facing both the
ultrasonic generation surface 31 and the liquid level 81.
Besides, in the fuel liquid level detecting apparatus 1B, the guide
pipe 4 is formed in the cylindrical shape whose sectional shape is
substantially uniform, but the whole inside surface of the guide
pipe 4 may well be formed in the shape of the conical surface as in
the first embodiment, so as to heighten the acoustic pressure level
of the ultrasonic wave entering the reflective surface 44.
Besides, the guide pipe 4 of the fuel liquid level detecting
apparatus 1B may well be provided with the correcting reflective
surface 41 as in the first embodiment, so as to compute the
propagation velocity of the ultrasonic wave within the fuel 8 and
to calculate the height of the liquid level 81 by utilizing the
computed propagation velocity.
(Third Embodiment)
As shown in FIG. 10, a fuel liquid level detecting apparatus 1C in
the third embodiment is such that a correcting reflective surface
(step) 41 to be stated later is provided inside the guide pipe
(first cylinder) 4 of the fuel liquid level detecting apparatus 1B
in the second embodiment, and that the baffle plate 9 inside the
guide pipe (second cylinder) 5 is omitted. Besides, likewise to the
bracket 15 of the fuel liquid level detecting apparatus 1A in the
first embodiment, the bracket 15 of the fuel liquid level detecting
apparatus 1C is formed in the state where the plug 13 is fitted
therein. The other constituents of the fuel liquid level detecting
apparatus 1C are constructed similarly to the corresponding
constituents of the fuel liquid level detecting apparatus 1B,
respectively.
In the guide pipe 4, a large-diameter portion 42 and a
small-diameter portion 43, which are cylindrical and which enclose
the ultrasonic-wave transmission route (first route) A between an
ultrasonic sensor 3 and a measuring reflective surface (reflector)
44, are located in the order of the large-diameter portion 42 and
the small-diameter portion 43 as viewed from the side of the
ultrasonic sensor 3. The diameter d42 of the large-diameter portion
42 is set to be larger than the diameter d43 of the small-diameter
portion 43, and the large-diameter portion 42 and the
small-diameter portion 43 are located coaxially with the ultrasonic
generation surface 31 of the ultrasonic sensor 3.
The correcting reflective surface 41 is formed at the joint part
between the large-diameter portion 42 and the small-diameter
portion 43 so as to oppose to the ultrasonic sensor 3, in other
words, perpendicularly to the traveling direction of an ultrasonic
wave in the transmission route A. The correcting reflective surface
41 defines an annular shape in which the outside diameter d42 and
the inside diameter d43 are coaxially located. Accordingly, part of
the ultrasonic wave generated from the ultrasonic sensor 3 falls on
the correcting reflective surface 41 by tracing a transmission
route C which is part of the transmission route A, it is reflected
there, and the reflected ultrasonic wave traces the transmission
route C again and is received by the ultrasonic sensor 3.
The operation of detecting a fuel liquid level 81 in the fuel
liquid level detecting apparatus 1C will be described.
When impressed with a pulse-shaped voltage signal by a pulse
generation circuit 101, the ultrasonic sensor 3 generates a
pulse-shaped ultrasonic wave into a fuel 8 within a fuel tank 2.
Then, the ultrasonic generation surface 31 of the ultrasonic sensor
3 vibrates, the vibration of the ultrasonic generation surface 31
is conveyed to the bottom 15b of the bracket 15, and an ultrasonic
wave is further generated from the outside surface 15a of the
bracket 15 into the fuel 8. Part of this ultrasonic wave proceeds
inside the guide pipe 4 by tracing the transmission route C shown
in FIG. 10, and enters the correcting reflective surface 41. The
partial ultrasonic wave is reflected there, and it enters the
ultrasonic generation surface 31 of the ultrasonic sensor 3 again
by tracing the transmission route C.
The remainder of the ultrasonic wave generated from the ultrasonic
sensor 3 into the fuel 8 proceeds inside the guide pipe 4 by
tracing the transmission route A and enters the measuring
reflective surface 44. The remainder ultrasonic wave is reflected
by the measuring reflective surface 44, and it proceeds inside a
guide pipe 5 and toward the liquid level 81 by tracing a
transmission route B. Further, it is reflected by the liquid level
81, and it enters the ultrasonic sensor 3 along the same route as
that of the going path, that is, via the transmission route B,
measuring reflective surface 44 and transmission route A again.
Thus, when the ultrasonic sensor 3 generates the single ultrasonic
pulse, it receives the two reflected pulses; the reflected pulse
from the correcting reflective surface 41 and the reflected pulse
from the liquid level 81. The length of the transmission route C
from the ultrasonic sensor 3 to the correcting reflective surface
41 is less than the length of a transmission route (A+B) from the
ultrasonic sensor 3 to the liquid level 81. Therefore, the
ultrasonic sensor 3 first receives the reflected pulse from the
correcting reflective surface 41 and subsequently receives the
reflected pulse from the liquid level 81. When the ultrasonic
sensor 3 receives the respective reflected pulses, it generates
voltage signals, which are inputted to an arithmetic circuit
102.
The arithmetic circuit 102 calculates time periods which are
expended since the issue of the pulse-shaped voltage signal by the
pulse generation circuit 101, till the detections of the two
reflected pulses stated above, respectively.
The relative position of the correcting reflective surface 41 to
the ultrasonic sensor 3 is fixed, and the distance between them is
known. Accordingly, the arithmetic circuit 102 calculates the
propagation velocity of the ultrasonic pulse within the fuel 8, on
the basis of the time period since the issue of the pulse-shaped
voltage signal by the pulse generation circuit 101 till the
reception of the reflected pulse from the correcting reflective
surface 41, and the distance between the correcting reflective
surface 41 and the ultrasonic sensor 3.
Subsequently, the arithmetic circuit 102 calculates the height H of
the liquid level 81, on the basis of the propagation velocity of
the ultrasonic pulse within the fuel 8 as thus calculated, and the
time period since the issue of the pulse-shaped voltage signal by
the pulse generation circuit 101 till the reception of the
reflected pulse from the liquid level 81. Further, the arithmetic
circuit 102 calculates the reserve of the fuel 8 within the fuel
tank 2, on the basis of the prestored shape of the fuel tank 2.
A drive circuit 103 outputs a signal for causing a display unit 110
to display the height H of the liquid level 81 or the reserve of
the fuel 8 as calculated by the arithmetic circuit 102, for
example, a drive signal for turning a needle shaft (not shown) up
to an angle which corresponds to the height H of the liquid level
81 or the reserve of the fuel 8. Thus, the height H of the liquid
level 81 in the fuel tank 2 or the reserve of the fuel 8 is
displayed by the display unit 110.
In the fuel liquid level detecting apparatus 1C, the ultrasonic
sensor 3 is directly fixed to the guide pipe 4 which is unitarily
provided with the correcting reflective surface 41.
Accordingly, the relative position between the ultrasonic sensor 3
and the correcting reflective surface 41 is kept highly accurate,
and the liquid level 81 of the fuel 8 can be detected at a high
accuracy.
Besides, the correcting reflective surface 41 is formed in the
annular shape in which the outside diameter d42 and the inside
diameter d43 lie coaxially with the ultrasonic sensor 3.
In general, the energy distribution of an ultrasonic wave generated
from the ultrasonic sensor 3 forms a shape of axial symmetry.
Therefore, when the correcting reflective surface 41 is located
coaxially with the ultrasonic sensor 3, a reflected wave, which
develops in such a way that the ultrasonic wave generated from the
ultrasonic sensor 3 is reflected by the reflective surface 41,
comes to have an energy distribution in the shape of axial symmetry
and is received by the ultrasonic sensor 3.
Thus, when the ultrasonic sensor 3 has received the reflected wave
from the reflective surface 41, it can output a stable detection
signal of high level, so that the ultrasonic propagation velocity
within the fuel 8 can be detected at a high accuracy. Accordingly,
the liquid level 81 of the fuel 8 can be detected at a high
accuracy.
Besides, in the fuel liquid level detecting apparatus 1C, the
reflective surface 44 which reflects the ultrasonic wave generated
from the ultrasonic sensor 3, toward the liquid level 81, is
provided at the end of the guide pipe 4 remote from the ultrasonic
sensor 3, unitarily with this guide pipe 4.
Thus, the relative position between the ultrasonic sensor 3 and the
measuring reflective surface 44, and an angle defined between the
ultrasonic sensor 3 and the measuring reflective surface 44 are
kept highly accurate, and the reflected wave reflected by the
liquid level 81 can be received by the ultrasonic sensor 3 without
fail, so as to reliably output the detection signal of the
reflected wave from the liquid level 81.
Besides, the fuel liquid level detecting apparatus 1C includes the
guide pipe 5 which encloses the ultrasonic transmission route B
between the measuring reflective surface 44 and the liquid level
81, and which is fixed to the guide pipe 4.
Accordingly, the ultrasonic wave generated from the ultrasonic
sensor 3 can be prevented from diffusing into the fuel tank 2 in
the course in which it is reflected by the measuring reflective
surface 44 so as to proceed toward the liquid level 81, or in the
course in which it is reflected by the liquid level 81 so as to
proceed toward the measuring reflective surface 44. Such diffusion
lowers the reception level of the ultrasonic sensor 3. Besides,
even when the liquid level 81 has quaked during the travel of an
automobile, the fluctuation of the liquid level 81 inside the guide
pipe 5 is suppressed to a low level. It is accordingly possible to
suppress the fluctuation of that indicated value of the display 110
which indicates the height H of the liquid level 81 (the reserve of
the fuel 8) within the fuel tank 2.
(Modification to Third Embodiment)
As shown in FIG. 13, the modification consists in altering the
shape of the correcting reflective surface (step) 41 of the fuel
liquid level detecting apparatus 1C. In the modification, the
correcting reflective surface (step) 41 is formed in the shape of a
conical surface the axis of which is identical to that of the
transmission route A.
In this case, an angle .theta. shown in FIG. 13 is set so that a
reflected wave reflected by the correcting reflective surface 41
may directly enter the ultrasonic sensor 3, whereby the same
effects as in the fuel liquid level detecting apparatus 1C are
attained.
In the fuel liquid level detecting apparatus 1C, the guide pipes 4
and 5 are formed as separate members, which are assembled together,
but they may well be unitarily formed.
Besides, the guide pipe 5 in the fuel liquid level detecting
apparatus 1C may well be omitted.
Besides, in the fuel liquid level detecting apparatus 1C, the
reflective surface 44 is shaped in a flat surface, but it may well
be shaped in a concave surface which is concave facing both the
ultrasonic generation surface 31 and the liquid level 81.
(Fourth Embodiment)
As shown in FIGS. 14 and 15, according to a fuel liquid level
detecting apparatus 1D in the fourth embodiment, a temperature
sensor (temperature detection means) 16 for detecting the
temperature of a fuel 8 is attached to the bracket 15 of the fuel
liquid level detecting apparatus 1C in the third embodiment.
Besides, in a control circuit 100, an arithmetic circuit 102
decides whether or not the fuel 8 with which a fuel tank 2 has been
replenished is of a predetermined kind. Light emitting diodes 113,
114 and a beeper 115 are connected to drive means 103 as report
means for notifying the results of the decisions. The other
constituents of the fuel liquid level detecting apparatus 1D are
constructed similarly to the corresponding constituents of the fuel
liquid level detecting apparatus 1C, respectively.
The temperature sensor 16 is constructed of a thermistor, and is
attached to the bracket 15. This temperature sensor 16 is connected
to an external electric circuit through a lead wire 16a.
The electric circuit arrangement of the fuel liquid level detecting
apparatus 1D will be described with reference to FIG. 15.
The arithmetic circuit 102 calculates the position of a liquid
level 81, and it also decides the kind of the fuel 8, namely, the
kind of a liquid. The red LED (light emitting diode) 113, orange
LED 114 and beeper 115 are connected as the report means to the
drive circuit 103. In case of the decision of the arithmetic
circuit 102 that the fuel 8 within the fuel tank 2 is not of the
predetermined kind, the drive circuit 103 drives the red LED 113 or
the orange LED 114 to turn ON, and it sounds the beeper 115,
thereby to give warning to the driver of an automobile.
Next, the operation of detecting the fuel liquid level in the fuel
liquid level detecting apparatus 1D will be described.
An ultrasonic sensor 3 is impressed with a pulse-shaped voltage
signal by a pulse generation circuit 101, and it generates a
pulse-shaped ultrasonic wave into the fuel 8 within the fuel tank
2. The ultrasonic generation surface 31 of the ultrasonic sensor 3
vibrates, the vibration of the ultrasonic generation surface 31 is
conveyed to the bottom 15b of the bracket 15, and an ultrasonic
wave is further generated from the outside surface 15a of the
bracket 15 into the fuel 8. Part of this ultrasonic wave proceeds
inside a guide pipe 4 by tracing a transmission route C shown in
FIG. 14, and enters a correcting reflective surface 41. The partial
ultrasonic wave is reflected there, and it enters the ultrasonic
generation surface 31 of the ultrasonic sensor 3 again by tracing
the transmission route C. On the other hand, part of the
pulse-shaped ultrasonic wave generated from the ultrasonic sensor 3
into the fuel 8 proceeds inside the guide pipe 4 by tracing a
transmission route A shown in FIG. 14 and enters a measuring
reflective surface 44. The partial ultrasonic wave is reflected by
the measuring reflective surface 44, and it proceeds inside a guide
pipe 5 and toward the liquid level 81 by tracing a transmission
route B shown in FIG. 14. Further, it is reflected by the liquid
level 81, and it enters the ultrasonic sensor 3 along the same
route as that of the going path, that is, via the transmission
route B, measuring reflective surface 44 and transmission route A
again.
Thus, when the ultrasonic sensor 3 is driven by the pulse
generation circuit 101 to generate the single ultrasonic pulse, it
receives the two reflected pulses; the reflected pulse from the
correcting reflective surface 41 and the reflected pulse from the
liquid level 81, in correspondence with the single-pulse generation
as stated above. As seen from FIG. 14, a transmission route length
from the ultrasonic sensor 3 to the correcting reflective surface
41 is less than a transmission route length from the ultrasonic
sensor 3 to the liquid level 81. Therefore, the ultrasonic sensor 3
first receives the reflected pulse from the correcting reflective
surface 41 and subsequently receives the reflected pulse from the
liquid level 81. When the ultrasonic sensor 3 receives the
respective reflected pulses, it generates voltage signals, which
are inputted to the arithmetic circuit 102.
The arithmetic circuit 102 calculates time periods which are
expended since the issue of the pulse-shaped voltage signal by the
pulse generation circuit 101, till the detections of the two
reflected pulses stated above, that is, a first round-trip time t1
being a time period in which the ultrasonic wave goes and comes
back between the ultrasonic sensor 3 and the correcting reflective
surface 41, and a second round-trip time t2 being a time period in
which the ultrasonic wave goes and comes back between the
ultrasonic sensor 3 and the liquid level 81 via the measuring
reflective surface 44, respectively.
Here, the correcting reflective surface 41 is provided at a
predetermined position relative to the ultrasonic sensor 3. That
is, the distance between the correcting reflective surface 41 and
the ultrasonic sensor 3 is known. Accordingly, the arithmetic
circuit 102 calculates a measured propagation velocity V1 being the
propagation velocity of the ultrasonic pulse in the fuel 8, on the
basis of the time period since the issue of the pulse-shaped
voltage signal by the pulse generation circuit 101 till the
reception of the reflected pulse from the correcting reflective
surface 41, and the distance between the correcting reflective
surface 41 and the ultrasonic sensor 3. Subsequently, the
arithmetic circuit 102 calculates the position of the liquid level
81, namely, the height H of the liquid level 81 in FIG. 14, on the
basis of the measured propagation velocity V1 being the propagation
velocity of the ultrasonic pulse in the fuel 8 as thus calculated,
and the second round-trip time t2 being the time period since the
issue of the pulse-shaped voltage signal by the pulse generation
circuit 101 till the reception of the reflected pulse from the
liquid level 81. Further, the arithmetic circuit 102 calculates the
reserve of the fuel 8 within the fuel tank 2, on the basis of the
prestored shape of the fuel tank 2.
Meanwhile, the propagation velocity of an ultrasonic pulse in a
liquid changes as the temperature of the liquid changes. In this
regard, in the fuel liquid level detecting apparatus 1D, the
correcting reflective surface 41 is provided to calculate the first
round-trip time t1, whereby the ultrasonic-pulse propagation
velocity in the fuel 8 at each point of time can be accurately
calculated. In the fuel liquid level detecting apparatus 1D,
accordingly, the data of the temperature of the fuel 8 as detected
by the temperature sensor 16 is not employed in the liquid-level
detecting operation.
The drive circuit 103 outputs a signal for causing a display unit
110 to display the height H of the liquid level 81 or the reserve
of the fuel 8 as calculated by the arithmetic circuit 102, for
example, a drive signal for turning a needle shaft (not shown) up
to an angle which corresponds to the height H of the liquid level
81 or the reserve of the fuel 8. Thus, the height H of the liquid
level 81 in the fuel tank 2 or the reserve of the fuel 8 is
displayed by the display unit 110.
Next, there will be described the operation of deciding the kind of
the liquid by the control circuit 100 as forms the characterizing
feature of the fuel liquid level detecting apparatus 1D.
Here in the fuel liquid level detecting apparatus 1D, the fuel 8 is
assumed to be gasoline. Then, in case of feeding oil into the fuel
tank 2 at a gasoline station, the regular fuel 8 is the gasoline,
and a fuel which might be erroneously fed is light oil.
In the fuel liquid level detecting apparatus 1D, accordingly, the
liquid decision circuit 102 of the control circuit 100 decides
whether the liquid in the fuel tank 2 is the gasoline, the light
oil, or water.
FIG. 16 is a flow chart for explaining the operation of the control
circuit 100 in the fuel liquid level detecting apparatus 1D.
At steps S101 through S108 in FIG. 16, the position of the liquid
level 81 is detected, a remaining fuel quantity R in the fuel tank
2 is calculated, and the remaining fuel quantity R is displayed on
the display unit 110. Subsequently, at steps S109 through S120 in
FIG. 16, the kind of the liquid in the fuel tank 2 is decided.
In the first place, there will be described the operations of the
detection of the liquid level 81--the display of the remaining fuel
quantity R as based on the control circuit 100 of the fuel liquid
level detecting apparatus 1D.
When an ignition switch 111 has been closed by the driver, the
control circuit 100 starts operating.
First, at the step S101, the pulse generation circuit 101 is driven
to generate an ultrasonic pulse from the ultrasonic sensor 3.
Subsequently, at the step S102, a reflected wave from the
correcting reflective surface 41, and a reflected wave from the
liquid level 81 via the measuring reflective surface 44 are
respectively detected by the arithmetic circuit 102.
Subsequently, at the step S103, the first round-trip time t1 being
the time period in which the ultrasonic pulse goes and comes back
between the ultrasonic sensor 3 and the correcting reflective
surface 41 is calculated by the arithmetic circuit 102.
Subsequently, at the step S104, the second round-trip time t2 being
the time period in which the ultrasonic pulse goes and comes back
between the ultrasonic sensor 3 and the liquid level 81 via the
measuring reflective surface 44 is calculated by the arithmetic
circuit 102.
Subsequently, at the step S105, a measured propagation velocity Va
which is the propagation velocity of the ultrasonic pulse in the
fuel 8 at this point of time is calculated on the basis of the
first round-trip time t1.
Subsequently, at the step S106, the position H of the liquid level
81 is calculated on the basis of the measured propagation velocity
Va.
Subsequently, at the step S107, the remaining fuel quantity R which
is a fuel reserve in the fuel tank 2 is calculated on the basis of
the position H of the liquid level 81.
Subsequently, at the step S108, the display unit 110 is driven by
the drive circuit 103 so as to display the remaining fuel quantity
R thereon.
The above is the liquid-level-81 detection operation--the
remaining-fuel-quantity-R display operation by the control circuit
100 of the fuel liquid level detecting apparatus 1D.
In the second place, there will be described the liquid-kind
decision operation by the control circuit 100 as forms the
characterizing feature of the fuel liquid level detecting apparatus
1D.
First, a fuel temperature Tf is detected at the step S109.
Subsequently, at the step S110, the measured propagation velocity
Va is corrected on the basis of the fuel temperature Tf by the
arithmetic circuit 102, whereby a corrected measured propagation
velocity Vc is calculated. Here in the fuel liquid level detecting
apparatus 1D, the corrected measured propagation velocity Vc is
calculated as a value at 20.degree. C.
Subsequently, at the step S111, the difference between the
corrected measured propagation velocity Vc and a reference
propagation velocity Vg being reference propagation velocity data
is calculated in the arithmetic circuit 102. The reference
propagation velocity Vg is the ultrasonic propagation velocity of
the fuel 8, namely, gasoline at 200C, and it is prestored in a
storage unit (not shown) within the arithmetic circuit 102.
On this occasion, if the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vg
lies within an error range E, it is decided that the corrected
measured propagation velocity Vc is substantially equal to the
reference propagation velocity Vg, in other words, that the fuel 8
is the gasoline.
It is accordingly unnecessary to actuate any of the red LED 113,
orange LED 114 and beeper 115 which are the report means.
Therefore, both the LEDs 113 and 114 are turned OFF at the step
S112, and the beeper 115 is stopped at the step S113.
If, at the step S111, the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vg
exceeds the error range E, it is judged that the fuel 8 is any
liquid other than the gasoline. Then, the control circuit 100
shifts to an operation for specifying the kind of the liquid as
will be explained below.
Subsequently, at the step S114, the difference between the
corrected measured propagation velocity Vc and a reference
propagation velocity Vd being reference propagation velocity data
is calculated in the arithmetic circuit 102. The reference
propagation velocity Vd is the ultrasonic propagation velocity of
light oil at 20.degree. C., and it is prestored in the storage unit
(not shown) within the arithmetic circuit 102.
On this occasion, if the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vd
lies within the error range E, it is decided that the corrected
measured propagation velocity Vc is substantially equal to the
reference propagation velocity Vd, in other words, that the fuel 8
is the light oil.
Accordingly, the arithmetic circuit 102 renders the decision that
the fuel 8 is the light oil, and it commands the drive circuit 103
to drive the red LED 113 and the beeper 115 which are the report
means.
When a gasoline engine has been fuelled with the light oil, it
becomes incapable of starting. It is therefore necessary to
promptly empty the fuel tank 2 and then supply the gasoline anew,
and to take such a measure as cleaning a fuel passage from the fuel
tank 2 to the engine and then filling up the passage with the
gasoline.
Consequently, the red LED 113 is turned ON at the step S115, and
also the beeper 115 is sounded at the step S116, whereby the driver
is reliably prompted to take the necessary measures.
If, at the step S114, the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vd
is greater the error range E, it is judged that the fuel 8 is any
liquid other than the gasoline and the light oil, and the step S117
is executed.
Here at the step S117, the difference between the corrected
measured propagation velocity Vc and a reference propagation
velocity Vw being reference propagation velocity data is calculated
in the arithmetic circuit 102. The reference propagation velocity
Vw is the ultrasonic propagation velocity of water at 20.degree.
C., and it is prestored in the storage unit (not shown) within the
arithmetic circuit 102.
On this occasion, if the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vw
is less than the error range E, it is decided that the corrected
measured propagation velocity Vc is substantially equal to the
reference propagation velocity Vw, in other words, that the liquid
8 is the water.
Accordingly, the arithmetic circuit 102 renders the decision that
the liquid 8 is the water, and it commands the drive circuit 103 to
drive the orange LED 114 and the beeper 115 which are the report
means.
Consequently, the orange LED 114 is turned ON at the step S118, and
also the beeper 115 is sounded at the step S119, whereby the driver
is reliably prompted to take necessary measures.
Here, it is usually impossible that the water be injected into the
fuel tank 2 in a fueling job. The stay of the water in the fuel
tank 2 is ascribable to the fact that waterdrops in a slight amount
have intruded through an oil feeding port in case of fueling on a
rainy day or the like, or that water vapor in the air within the
fuel tank 2 has formed dewdrops due to a temperature fall and has
mixed into the fuel 8. Besides, since the specific weight of the
water is greater than that of the fuel 8, namely, the gasoline or
the light oil, the water stays in the bottom of the fuel tank 2. In
other words, the water stays at the peripheral part of the fuel
liquid level detecting apparatus 1D, for example, within the guide
pipe 4.
Thus, when the quantity of the water staying in the fuel tank 2 has
reached a certain quantity, the fuel liquid level detecting
apparatus 1D can reliably detect the situation as stated above.
If, at the step S117, the difference between the corrected measured
propagation velocity Vc and the reference propagation velocity Vw
is greater than the error range E, it is judged that the fuel 8 is
any liquid other than the gasoline, the light oil and the
water.
In this case, the driver needs to promptly check what is the liquid
within the fuel tank 2.
Therefore, the arithmetic circuit 102 issues a command to the drive
circuit 103 so as to simultaneously turn ON the red LED 113 and the
orange LED 114 at the step S120.
In the fuel liquid level detecting apparatus 1D described above,
the measured propagation velocity Va being the ultrasonic
propagation velocity in the fuel 8 as calculated in the course of
the liquid level detecting operation is corrected to the value at
20.degree. C., on the basis of the fuel temperature Tf, whereby the
corrected measured propagation velocity Vc is calculated. On the
other hand, in the control circuit 100, the ultrasonic propagation
velocities in the several liquids, for example, the gasoline, light
oil and water at 20.degree. C. are prestored as the reference
propagation velocity data. Besides, the corrected measured
propagation velocity Vc is compared with the respective reference
propagation velocities Vg, Vd and Vw, whereby the kind of the
liquid in the fuel tank 2 is distinguishable. That is, it is
decided that the liquid whose reference propagation velocity is
equal to or nearest to the corrected measured propagation velocity
Vc is the liquid in the tank.
Thus, the kind of the liquid in the fuel tank 2 can be
discriminated easily and accurately. It is therefore possible to
realize the fuel liquid level detecting apparatus 1D which can
prevent the occurrence of any drawback ascribable to the actuation
of the automobile in the state where the liquid of the kind
different from the predetermined liquid or the gasoline, has been
injected into the fuel tank 2 or has mixed thereinto.
Here in the fuel liquid level detecting apparatus 1D, the
comparison of the propagation velocities of the ultrasonic wave is
made using the data at 20.degree. C. That is, the comparison is
made under the same temperature condition. Thus, the liquid can be
discriminated at a high accuracy.
By the way, in such a case where the range of the changes of the
fuel temperature within the fuel tank 2 is limited, the temperature
sensor 16 may well be omitted so as to discriminate the liquid by
using the measured propagation velocity Va, not the corrected
measured propagation velocity Vc.
(Fifth Embodiment)
Shown in FIG. 17 is a flow chart for explaining the operation of a
control circuit 100 in a fuel liquid level detecting apparatus 1D
in the fifth embodiment. By the way, in FIG. 17, parts relevant to
a liquid level detecting operation, namely, steps S101 S108 are
omitted because they are the same as in the fourth embodiment.
In the fuel liquid level detecting apparatus 1D of the fourth
embodiment, the discrimination of the liquid kind is done on the
basis of the ultrasonic propagation velocities in the liquid 8. In
contrast, in the fuel liquid level detecting apparatus 1D of the
fifth embodiment, the liquid discrimination is implemented on the
basis of a first round-trip time t1 being a time period in which an
ultrasonic wave goes and comes back between an ultrasonic sensor 3
and a correcting reflective surface 41.
Hereinbelow, the same parts as in the fuel liquid level detecting
apparatus 1D of the fourth embodiment shall be omitted from
description, and only parts peculiar to the fuel liquid level
detecting apparatus 1D of the fifth embodiment will be
described.
As shown in FIG. 17, at a step S121, the first round-trip time t1
is corrected on the basis of a fuel temperature Tf detected at a
step S109, thereby to calculate a corrected round-trip time tc.
Here in the fuel liquid level detecting apparatus 1D of the fifth
embodiment, the corrected round-trip time tc is calculated as a
value at 20.degree. C.
Subsequently, at a step S122, the difference between the corrected
round-trip time tc and a reference round-trip time tg being
reference round-trip time data is calculated in an arithmetic
circuit 102. The reference round-trip time tg is a first round-trip
time at 20.degree. C. in the case where the fuel 8 is gasoline, and
it is prestored in a storage unit (not shown) within the arithmetic
circuit 102.
On this occasion, if the difference between the corrected
round-trip time tc and the reference round-trip time tg is less
than an error range F, it is decided that the corrected round-trip
time tc is substantially equal to the reference round-trip time tg,
in other words, that the fuel 8 is the gasoline.
It is accordingly unnecessary to actuate any of a red LED 113, an
orange LED 114 and a beeper 115 which are report means. Therefore,
both the LEDs 113 and 114 are turned OFF at a step S123, and the
beeper 115 is stopped at a step S124.
If, at the step S122, the difference between the corrected
round-trip time tc and the reference round-trip time tg is greater
than the error range F, it is judged that the fuel 8 is any liquid
other than the gasoline. Then, the control circuit 100 shifts to an
operation for specifying the kind of the liquid as will be
explained below.
Subsequently, at a step S125, the difference between the corrected
round-trip time tc and a reference round-trip time td being
reference round-trip time data is calculated in the arithmetic
circuit 102. The reference round-trip time td is a first round-trip
time at 20.degree. C. in the case where the fuel 8 is light oil,
and it is prestored in the storage unit (not shown) within the
arithmetic circuit 102.
On this occasion, if the difference between the corrected
round-trip time tc and the reference round-trip time td is less
than the error range F, it is decided that the corrected round-trip
time tc is substantially equal to the reference round-trip time td,
in other words, that the fuel. 8 is the light oil.
Thus, the arithmetic circuit 102 renders the decision that the fuel
8 is the light oil, and it commands a drive circuit 103 to drive
the red LED 113 and beeper 115 which are the report means.
Consequently, the red LED 113 is turned ON at a step S126, and also
the beeper 115 is sounded at a step S127, whereby the driver of an
automobile can be reliably prompted to take necessary measures.
If, at the step S125, the difference between the corrected
round-trip time tc and the reference round-trip time td is greater
than the error range F, it is judged that the fuel 8 is any liquid
other than the gasoline and the light oil, followed by a step
S128.
Here at the step S128, the difference between the corrected
round-trip time tc and a reference round-trip time tw being
reference round-trip time data is calculated in the arithmetic
circuit 102. The reference round-trip time tw is a first round-trip
time at 20.degree. C. in the case of water, and it is prestored in
the storage unit (not shown) within the arithmetic circuit 102.
On this occasion, if the difference between the corrected
round-trip time tc and the reference round-trip time tw is less
than the error range F, it is decided that the corrected round-trip
time tc is substantially equal to the reference round-trip time td,
in other words, that the liquid 8 is the water.
Thus, the arithmetic circuit 102 renders the decision that the
liquid 8 is the water, and it commands the drive circuit 103 to
drive the orange LED 114 and beeper 115 which are the report means.
Consequently, the orange LED 114 is turned ON at a step S129, and
also the beeper 115 is sounded at a step S130, whereby the driver
can be reliably prompted to take necessary measures.
If, at the step S128, the difference between the corrected
round-trip time tc and the reference round-trip time tw is greater
than the error range F, it is judged that the fuel 8 is any liquid
other than the gasoline, the light oil and the water.
In this case, the driver needs to promptly check what is the liquid
within the fuel tank 2.
Therefore, the arithmetic circuit 102 issues a command to the drive
circuit 103 so as to simultaneously turn ON the red LED 113 and the
orange LED 114 at a step S131.
As described above, also the fuel liquid level detecting apparatus
1D of the fifth embodiment can discriminate the kind of the liquid
in the fuel tank 2 easily and accurately. Therefore, it is reliably
found that the liquid of the kind different from the predetermined
liquid or the gasoline has been injected into the fuel tank 2.
Incidentally, each of the fuel liquid level detecting apparatuses
1D in the fourth and fifth embodiments is constructed so that the
liquid kind discriminating operation may be performed integrally
with and continuously to the liquid level position detecting
operation. However, the liquid level position detecting operation
need not always be performed, but it may well be executed at
limited timings in accordance with predetermined rules. By way of
example, although no illustration is made, the liquid level
position detecting operation may well be executed one time--several
times immediately after the ignition switch 111 has been closed by
the driver. Alternatively, the liquid level position detecting
operation may well be executed one time--several times immediately
after the ignition switch 111 has been closed by the driver
subsequently to the replenishment of the fuel tank 2 with the fuel
8. In this case, the replenishment of the fuel tank 2 with the fuel
8 can be detected by, for example, disposing a sensor which detects
that the lid of the fuel feeding port of the automobile has been
opened and shut.
Besides, in each of the fuel liquid level detecting apparatuses 1D
according to the first and second embodiments of the invention as
described before, the red LED 113 and the orange LED 114 are
employed as the report means. However, the colors of light
emissions need not be restricted to the exemplary ones, but other
colors may well be adopted. Also, a display unit (not shown) as
report means may well be formed by performing a translucent
coloring process in a character panel (not shown) on which the
display unit 110, etc. are to be installed. In that case, the red
LED 113 and orange LED 114 may well be substituted by white LEDs,
electric bulbs or the likes. Alternatively, the behavior of the
fuel, namely, the kind of the fuel may, of course, be delivered as
a message by a liquid crystal display.
Besides, in each of the fuel liquid level detecting apparatuses 1D
in the fourth and fifth embodiments, the beeper 115 is employed as
the report means. However, the beeper 115 need not be restricted to
a beeper of so-called "electromagnetic type", but several warning
sounds may well be synthesized by an electronic circuit so as to be
emitted by a loudspeaker or the like.
(Sixth Embodiment)
Shown in FIG. 18 is a partial sectional view of a fuel tank 2 which
is furnished with a fuel liquid level detecting apparatus 1E in the
sixth embodiment. By the way, in FIG. 18, the same reference
numerals are respectively assigned to the same parts as in FIG.
14.
In the fuel liquid level detecting apparatus 1E of the sixth
embodiment, the guide pipe 4 in the fuel liquid level detecting
apparatus 1D of the fourth embodiment is done away with, and the
ultrasonic sensor 3 is fixed at the lower end part of the guide
pipe 5. Besides, the ultrasonic sensor 3 is attached in an attitude
in which it can generate an ultrasonic wave directly toward a
liquid level 81 as shown in FIG. 18.
In the fuel liquid level detecting apparatus 1E, the ultrasonic
sensor 3 generates the ultrasonic wave therefrom and receives a
reflected wave from the liquid level 81. Thus, the detecting
apparatus 1E calculates a time period in which the ultrasonic wave
makes a round trip between the ultrasonic sensor 3 and the liquid
level 81, and it detects the liquid level 81 on the basis of the
calculated time period.
Besides, in the fuel liquid level detecting apparatus 1E, a liquid
kind discriminating operation is executed only immediately after
the fuel tank 2 has been fed with a fuel 8.
In the job of feeding the fuel 8 for an automobile, the fuel tank 2
is generally brought into a full tank state. Besides, the position
of the highest liquid level 82 as is a liquid level position in the
full tank state is substantially identical every fuel feeding job,
and the distance between the ultrasonic generation surface 31 of
the ultrasonic sensor 3 and the highest liquid level 82 is a known
value.
Accordingly, the kind of any liquid fed into the fuel tank 2 can be
reliably discriminated in such a way that a measured round-trip
time, which is the round-trip time period of the ultrasonic wave
between the ultrasonic generation surface 31 of the ultrasonic
sensor 3 and the highest liquid level 82 as has been measured
immediately after the fuel feeding, is compared with reference
round-trip times, which are the round-trip time periods between the
ultrasonic generation surface 31 and the highest liquid level 82
within various liquids (fuels) as are prestored in a control
circuit 100.
Usually, during the fuel feeding job, an ignition switch 111 is
kept turned-OFF for the sake of safety. Besides, the completion of
the fuel feeding into the fuel tank 2 can be sensed by such a
method as detecting the opening and shutting of the lid of an oil
feeding port, or detecting the attachment and detachment of an oil
feeding nozzle to and from the oil feeding port.
Here in the fuel liquid level detecting apparatus 1E of the sixth
embodiment, the liquid kind discriminating operation is implemented
at the point of time at which the ignition switch 111 has been
first turned ON after the detection of the completion of the fuel
feeding into the fuel tank 2.
Thus, also in the fuel liquid level detecting apparatus 1E, the
kind of the liquid in the fuel tank 2 can be discriminated easily
and accurately.
Incidentally, a probability at which any liquid other than a
regular fuel mixes into the fuel tank 2 of the automobile is the
maximum in the fuel feeding job, so that even the liquid kind
discriminating operation in the fuel liquid level detecting
apparatus 1E is satisfactory in practical use.
Besides, it is needless to say that the liquid behavior
discriminating apparatus of the invention is also applicable to a
liquid level detecting apparatus which does not include a measuring
reflective member or a calibrating reflective member as in each of
the fuel liquid level detecting apparatuses according to the fourth
and fifth embodiments, and which generates an ultrasonic wave from
an ultrasonic generation sensor into a liquid and measures a time
period expended since the generation of the ultrasonic wave by the
ultrasonic generation sensor, till the reception of a reflected
wave reflected by the liquid level of the liquid, thereby to detect
the liquid level position of the liquid (refer, for example, to
JP2001-208595A).
(Seventh Embodiment)
As shown in FIG. 19, according to a fuel liquid level detecting
apparatus 1F in the seventh embodiment, the guide pipe 5 of the
fuel liquid level detecting apparatus 1C in the third embodiment is
constructed in such a way that a lower pipe 5A and an upper pipe 5B
are coupled by a spring (elastic member) 5C. The other constituents
of the fuel liquid level detecting apparatus 1F are constructed
similarly to the corresponding constituents of the fuel liquid
level detecting apparatus 1C, respectively.
Each of the lower pipe 5A and upper pipe 5B is formed of a circular
tube which is made from stainless steel. The outside dimension and
inside diameter dimension of the lower pipe 5A are respectively
equal to those of the upper pipe 5B. The spring 5C is a
close-coiled spring which is formed of a spring steel wire.
The elastic coefficient of the spring 5C is set to be much smaller
than that of the lower pipe 5A as well as the upper pipe 5B.
Besides, the inside diameter dimension of the spring 5C per se is
set to be slightly smaller than the outside dimension of the lower
pipe 5A as well as the upper pipe 5B. Thus, in a state where the
lower pipe 5A and the upper pipe 5B are butted against each other,
the spring 5C is snugly fitted on these pipes 5A and 5B so as to
cover the joint part between both these pipes, whereby the lower
pipe 5A and the upper pipe 5B are connected by the restoring force
of the spring 5C.
Usually, a fuel liquid level detecting apparatus is attached into a
fuel tank 2 after the apparatus itself has been assembled up.
Besides, the job of attaching the fuel liquid level detecting
apparatus into the fuel tank 2 is performed through, for example,
an opening (not shown) for inserting a fuel pump (not shown) to be
mounted inside the fuel tank 2, into this fuel tank 2 as in the
fuel liquid level detecting apparatus 1F. The size of the opening
is set to be small to the utmost within a range within which the
job is possible. It is accordingly difficult to put the fuel liquid
level detecting apparatus 1F into the fuel tank 2, the interior of
which cannot be seen, through the opening, and to fix the detecting
apparatus 1F to a predetermined position and in a predetermined
attitude.
The guide pipe 5 of the fuel liquid level detecting apparatus 1F
has its distal end protruded above a liquid level in a full tank
condition, namely, the highest liquid level 82. That is, in a state
where the fuel liquid level detecting apparatus 1F has been fixed
in the fuel tank 2, the guide pipe 5 occupies substantially the
full length of the fuel tank 2 in the depth direction thereof.
For this reason, in the prior-art liquid level detecting apparatus,
there has been the possibility of the occurrence of the drawback
that, in the job of the attachment into the fuel tank 2, the distal
end of the guide pipe 5 will touch and damage the fuel tank 2.
In contrast, according to the fuel liquid level detecting apparatus
1F of the seventh embodiment, the guide pipe 5 is divided into the
two elements, namely, the lower pipe 5A and the upper pipe 5B in
its axial direction, namely, in the vertical direction of the fuel
tank 2, and both the pipes 5A and 5B are unitarily fixed by the
spring 5C.
Here, the spring constant of the spring 5C is set to be much
smaller than the elastic coefficient of the lower pipe 5A as well
as the upper pipe 5B. In other words, in a case where any external
force has acted on the guide pipe 5, the lower pipe 5A and the
upper pipe 5B are hardly deformed, and the spring 5C is
deformed.
When the guide pipe 5 has touched the fuel tank 2 in the job of
attaching the fuel liquid level detecting apparatus 1F to the fuel
tank 2, the spring 5C is deformed, and the guide pipe 5 buckles
with the spring 5C as an articulation.
Thus, the force acting on the fuel tank 2 decreases abruptly, and
the fuel tank 2 can be prevented from being damaged by the guide
pipe 5 of the fuel liquid level detecting apparatus 1F.
Further, when the external force acting on the guide pipe 5 has
become extinct upon the completion of the attaching job of the fuel
liquid level detecting apparatus 1F, the guide pipe 5 is restored
into its original shape by the restoring force of the spring 5C.
Consequently, the guide pipe 5 reliably plays the role of the
ultrasonic transmission route between a measuring reflective
surface 44 and a liquid level 81 in the fuel liquid level detecting
apparatus 1F, so that the fuel liquid level detecting apparatus 1F
operates normally.
In the fuel liquid level detecting apparatus 1F, the dynamical
characteristics of the spring 5C which couples the lower pipe 5A
and the upper pipe 5B are set, for example, so as to satisfy the
following conditions: The guide pipe 5 is not deformed even when it
has undergone the jolting of an automobile attributed to the travel
thereof, the wave energy of the quaking liquid level, etc. In
addition, when the guide pipe 5 has touched the fuel tank 2 in the
job of attaching the fuel liquid level detecting apparatus 1F to
the fuel tank 2, the spring 5C is deformed before the magnitude of
the force acting on the fuel tank 2 by the guide pipe 5 reaches a
level at which the fuel tank 2 is damaged.
(Eighth Embodiment)
As shown in FIG. 21, a fuel liquid level detecting apparatus 1G in
the eighth embodiment is such that a guard cap 17 is installed on
the upper end of the guide pipe 5 of the fuel liquid level
detecting apparatus 1F in the seventh embodiment. The other
constituents of the fuel liquid level detecting apparatus 1G are
constructed similarly to the corresponding constituents of the fuel
liquid level detecting apparatus 1F (1C), respectively.
The guard cap 17 is formed from rubber or a resin material, and is
snugly fitted on the upper end of the guide pipe 5 (upper pipe 5B).
This guard cap 17 is formed with a protuberance 17a which extends
in the axial extending direction of the guide pipe 5, that is,
upwards in FIG. 21. The protuberance 17a is provided outside the
contour lines of the upper pipe 5B (broken lines in FIG. 21) as
shown in FIG. 22 which is a view seen along arrow XXII in FIG. 21.
Further, the guard cap 17 is provided with a through hole 17b which
communicates the inside of the guide pipe 5 with the interior of a
fuel tank 2.
In the job of attaching the fuel liquid level detecting apparatus
1G to the fuel tank 2, when the guide pipe 5 has touched the fuel
tank 2, the protuberance 17a of the guard cap 17 first comes into
touch with the fuel tank 2. Here, the protuberance 17a is disposed
outside the contour lines of the upper pipe 5B (broken lines in
FIG. 22). Therefore, a bending moment which acts on the guide pipe
5, namely, a moment which acts so that a lower pipe 5A and the
upper pipe 5B may buckle with a spring 5C as an articulation,
becomes greater than in the case of the fuel liquid level detecting
apparatus 1F according to the seventh embodiment.
Thus, the lower pipe 5A and the upper pipe 5B buckle with the
spring 5C as the articulation, at the point of time at which a
contact force is smaller. That is, owing to the touch of the distal
end of the upper pipe 5B with the fuel tank 2, forces which act on
the guide pipe 5 and the fuel tank 2 can be sharply decreased.
Accordingly, the fuel tank 2 can be reliably prevented from being
damaged by the guide pipe 5 of the fuel liquid level detecting
apparatus 1G.
(Ninth Embodiment)
As shown in FIG. 23, a fuel liquid level detecting apparatus 1H in
the ninth embodiment is such that the lower pipe 5A and upper pipe
5B of the fuel liquid level detecting apparatus 1F in the seventh
embodiment are connected by a rubber pipe 5D instead of the spring
5C. The other constituents of the fuel liquid level detecting
apparatus 1H are constructed similarly to the corresponding
constituents of the fuel liquid level detecting apparatus 1F (1C),
respectively.
Also in this case, the same effects as in the case of the fuel
liquid level detecting apparatus 1F of the seventh embodiment are
attained.
In the fuel liquid level detecting apparatus 1H, a material which
is highly anticorrosive against a fuel 8 is chosen for the rubber
pipe 5D. Besides, the dynamical characteristics of the rubber pipe
5D as the spring are set so as to fulfill the same conditions as in
the case of the spring 5C in the fuel liquid level detecting
apparatus 1F of the seventh embodiment.
(Tenth Embodiment)
As shown in FIG. 24, a fuel liquid level detecting apparatus 11 in
the tenth embodiment is such that the guide pipe 5 of the fuel
liquid level detecting apparatus 1F in the seventh embodiment is
constructed of a single member, and that three annular grooves 5a
are formed in the outer periphery of the guide pipe 5. The other
constituents of the fuel liquid level detecting apparatus 11 are
constructed similarly to the corresponding constituents of the fuel
liquid level detecting apparatus 1F (1C), respectively.
In the job of attaching the fuel liquid level detecting apparatus
11 to a fuel tank 2, when the guide pipe 5 has touched the fuel
tank 2, bending stresses develop in the guide pipe 5. Since,
however, stress concentrations occur at the parts of the annular
grooves 5a, the bending stresses at these parts become much greater
than the bending stresses at the other parts of the guide pipe 5.
That is, the guide pipe 5 is deformed and buckled at the part of
the annular groove 5a, so that the same effects as in the seventh
embodiment are attained.
Incidentally, although the number of the annular grooves 5a is
three in the fuel liquid level detecting apparatus 1I, a single
annular groove, or two or at least four annular grooves may well be
provided.
(Modification to Seventh Embodiment)
As shown in FIG. 25, a modification to the fuel liquid level
detecting apparatus 1F of the seventh embodiment is such that the
lower pipe 5A and upper pipe 5B in the fuel liquid level detecting
apparatus 1F of the seventh embodiment are formed of tubular
members which have different outside dimensions and inside diameter
dimensions, and that one of the pipes is inserted into the other,
whereupon a spring 5E is held in close touch with the outer
periphery of the insertion part of the pipes. The other
constituents of the fuel liquid level detecting apparatus 1F are
constructed similarly to the corresponding constituents of the fuel
liquid level detecting apparatus 1F (1C), respectively.
The lower pipe 5A and the upper pipe 5B are insertionally assembled
so as to be slidable to each other. The spring 5E held in close
touch with the outer periphery of the insertion part is such that
both its end parts are close-coiled parts 5Ea, while its middle
part is a loosely-coiled part 5Eb in the shape of a compression
spring. Both the close-coiled parts 5Ea are respectively held in
close touch with the lower pipe 5A and the upper pipe 5B.
In the job of attaching the fuel liquid level detecting apparatus
1F to a fuel tank 2, when a guide pipe 5 has touched the fuel tank
2, the upper pipe 5B slides relative to the lower pipe 5A while
resisting the restoring force of the loosely-coiled part 5Eb of the
spring 5E, thereby to move downwards in FIG. 25.
Accordingly, the same effects as in the fuel liquid level detecting
apparatus 1F of the seventh embodiment are attained.
Although a step arises on the inner surface of the guide pipe 5 in
the modification to the fuel liquid level detecting apparatus 1F of
the seventh embodiment, it does not reflect an ultrasonic wave
proceeding from a measuring reflective surface 44 toward a liquid
level 81, onto the side of the measuring reflective surface 44.
Accordingly, the position of the liquid level 81 is detectable at a
high accuracy even in the modification to the fuel liquid level
detecting apparatus 1F of the seventh embodiment.
By the way, in each of the fuel liquid level detecting apparatuses
1F 1I of the seventh tenth embodiments, the guide pipe 4 is formed
from an aluminum die casting alloy, while the guide pipe 5 is
formed of a stainless steel pipe. However, the guide pipes 4 and 5
may well be formed from other substances.
Besides, in each of the fuel liquid level detecting apparatuses 1F
1I of the seventh tenth embodiments, the measuring reflective
surface 44 is shaped in a flat surface, but it may well be shaped
in a concave surface which is concave facing both the ultrasonic
generation surface 31 and the liquid level 81.
Besides, in each of the fuel liquid level detecting apparatuses 1F
1I of the seventh tenth embodiments, the ultrasonic sensor 3 is
installed with the ultrasonic generation direction of the
ultrasonic wave held in parallel with the liquid level 81, and the
guide pipe 4 is provided with the measuring reflective surface 44,
thereby to reflect the ultrasonic wave toward the liquid level 81.
However, the ultrasonic sensor 3 may well be installed at the lower
end of the guide pipe 5, that is, at the lower end of the lower
pipe 5A, by omitting the guide pipe 4 and the measuring reflective
surface 44, so as to transmit the ultrasonic wave from the
ultrasonic sensor 3 directly toward the liquid level 81 inside the
guide pipe 5.
Besides, the guide pipe 4 is provided with the correcting
reflective surface 41 in each of the fuel liquid level detecting
apparatuses 1F 1I of the seventh tenth embodiments, but the
correcting reflective surface 41 need not always be formed. In this
case, the liquid level 81 may well be calculated by correcting the
propagation velocity of the ultrasonic wave in the fuel 8 on the
basis of a temperature detection signal which is generated by an
air temperature sensor (not shown) mounted in the automobile, or a
temperature detection signal which is obtained by installing a fuel
temperature sensor in the fuel tank 2.
(Eleventh Embodiment)
As shown in FIGS. 26 and 27, a fuel liquid level detecting
apparatus 1J in the eleventh embodiment is such that the ultrasonic
sensor 3 of the fuel liquid level detecting apparatus 1B in the
second embodiment is not fixed to the bottom 15b of the bracket 15
by bonding or the like, but that it is fixed by being held between
the bracket 15 and the plug 13 fitted in this bracket, owing to the
restoring force of a spring 18. The other constituents of the fuel
liquid level detecting apparatus 1J are constructed similarly to
the corresponding constituents of the fuel liquid level detecting
apparatus 1B, respectively.
The ultrasonic sensor 3 is constructed similarly to the ultrasonic
sensor 3 of the fuel liquid level detecting apparatus 1A in the
first embodiment. The bracket 15 is formed substantially in the
shape of a bottomed cylinder from a resin material or a metal
material. In the bracket 15, the ultrasonic sensor 3 is located so
as to have its ultrasonic generation surface 31 held in close touch
with the bottom 15b of the bracket 15.
The plug 13 formed from a resin material or the like is fixed on
the opposite side to the bottom 15b of the bracket 15 (right side
in FIG. 26) in such a way that the protuberance 13a thereof is held
in engagement with the engaging portion 15e of the bracket 15.
The spring (elastic member) 18 is interposed between the ultrasonic
sensor 3 and the plug 13. This spring 18 is a coiled spring and is
compressed in a state where it is assembled in the bracket 15, and
the restoring force thereof acts in a direction indicated by a
double-headed arrow in FIG. 27. Owing to the elastic force, the
ultrasonic sensor 3 is brought into close touch with the bottom 15b
of the bracket 15.
The plug 13 is provided with through holes 13b, 13c. The air having
accumulated in the bracket 15 is discharged out through the through
hole 13b. Besides, the lead wire 14 of the ultrasonic sensor 3 is
led out of the bracket 15 through the through hole 13c.
Besides, the bracket 15 is formed with through holes 15c which
communicate the front surface 15a and bottom 15b of this bracket.
The through holes 15c are respectively provided in the upper and
lower parts of the bracket 15 in a state where the fuel liquid
level detecting apparatus 1J has been attached to a fuel tank 2. As
shown in FIG. 27, the through holes 15c are open at positions which
overlap the ultrasonic generation surface 31 of the ultrasonic
sensor 3. Besides, the minimum distance F between the surface 47 of
a guide pipe 4 and the front surface 15a of the bracket 15 is set
to be greater than the diametric dimension d15c of each through
hole 15c in a state where the bracket 15 has been fixed to the
guide pipe 4. The bracket 15 is fixed to the guide pipe 4 in such a
way that the protuberance 15d thereof is held in engagement with
the engaging portion 48 of the guide pipe 4.
In the case of fixing the ultrasonic sensor to the bottom of the
bracket with an adhesive, the air must be prevented from mixing
into the adhesive layer between the ultrasonic sensor and the wall
surface of the bracket in such a way that the viscosity,
temperature and coating method of the adhesive are managed to the
optima during a bonding job, and that the held attitude of the
ultrasonic sensor is appropriately managed after the bonding of the
adhesive till the hardening thereof. Therefore, increase in the
number of man-hour and consequent increase in the cost of
production are incurred.
In this regard, in the fuel liquid level detecting apparatus 1J,
the ultrasonic sensor 3 is urged against and fixed to the bottom
15b of the bracket 15 by the restoring force of the spring 18
without using the adhesive or the like. Besides, the bracket 15 is
provided with the through holes 15c which communicate the bottom
15b and the front surface 15a of this bracket, and a part of which
overlaps the ultrasonic generation surface 31 of the ultrasonic
sensor 3.
Microscopically, the ultrasonic generation surface 31 of the
ultrasonic sensor 3 and the bottom 15b of the bracket 15 are not
perfect flat surfaces, but they have minute ruggedness as shown in
FIG. 27. Accordingly, the ultrasonic generation surface 31 and the
bottom 15b are not perfectly held in close touch, but a minute gap
G2 is formed between both the portions.
Immediately after the fuel liquid level detecting apparatus 1J has
been attached into the fuel tank 2, the air exists in the gap
between the ultrasonic generation surface 31 and the bottom 15b.
When a fuel 8 has been thereafter injected into the fuel tank 2,
the guide pipe 4 and the bracket 15 are immersed in the fuel 8. On
this occasion, the fuel 8 fills up the guide portion 42 of the
guide pipe 4, and it flows into the bracket 15 through the through
holes 15c of this bracket 15 to arrive at the close touch portion
between the ultrasonic generation surface 31 and the bottom 15b.
The fuel 8 enters the gap G2 between the ultrasonic generation
surface 31 and the bottom 15b by a capillary action until this gap
G2 is completely filled up with the fuel 8.
Thus, in the close touch portion between the ultrasonic generation
surface 31 and the bottom 15b, the fuel 8 intervenes except in
parts at which both the portions 31 and 15b are really held in
touch, so that the vibration of the ultrasonic sensor 3 is conveyed
to the bracket 15 through the fuel 8, not through the air.
Accordingly, the vibration energy of the ultrasonic sensor 3 can be
efficiently conveyed to the bracket 15, so that an ultrasonic wave
generated from the ultrasonic sensor 3 can be transmitted into the
fuel 8 at a high efficiency with the cost increases suppressed.
Besides, the through holes 15c are respectively provided in the
upper and lower parts of the bracket 15.
Accordingly, when the fuel tank 2 is replenished with the fuel 8,
the air having stayed in the bracket 15 is effectively discharged
out of this bracket through the through holes 15c, and the gap G2
between the ultrasonic generation surface 31 and the bottom 15b is
completely filled up with the fuel 8.
Besides, in the state where the bracket 15 has been fixed to the
guide pipe 4, the minimum distance F between the surface 47 of the
guide pipe 4 and the front surface 15a of the bracket 15 is set to
be greater than the diametric dimension d15c of each through hole
15c.
In a case where the minimum distance F between the surface 47 of
the guide pipe 4 and the front surface 15a of the bracket 15 is
smaller than the diametric dimension d15c of each through hole 15c,
and where the fuel tank 2 is replenished with the fuel 8 in a state
in which the gap G2 between the ultrasonic generation surface 31
and the bottom 15b is not filled up the fuel 8, the fuel 8 enters
the interspace between the surface 47 and the front surface 15a
owing to the capillary action, but the fuel 8 in the interspace is
drawn by surface tensions and does not enter the through holes 15c.
That is, the fuel 8 does not enter the bracket 15, and the gap G2
between the ultrasonic generation surface 31 and the bottom 15b is
not sufficiently filled with the fuel 8.
Since, in the fuel liquid level detecting apparatus 1J, the minimum
distance F between the surface 47 of the guide pipe 4 and the front
surface 15a of the bracket 15 is set to be greater than the
diametric dimension d15c of each through hole 15c, the fuel 8
having entered the interspace between the surface 47 and the front
surface 15a flows into the through holes 15c with ease, and the gap
G2 between the ultrasonic generation surface 31 and the bottom 15b
is sufficiently filled with the fuel 8.
When the fuel 8 has been consumed to substantially empty the fuel
tank 2, the fuel 8 remains while filling up the guide portion 42 of
the guide pipe 4, in some cases, and the air enters the guide
portion 42 of the guide pipe 4 in the other cases, depending upon
the shapes of the fuel tank 2. Even in the case where the air
enters the guide portion 42 of the guide pipe 4, the fuel 8 which
lies in the gap G2 between the ultrasonic generation surface 31 of
the ultrasonic sensor 3 and the bottom 15b of the bracket 15 is
still held in the gap G2 under the action of surface tensions.
Besides, even in a case where the air has entered part of the gap
G2 due to the jolting of an automobile, or the like, this gap G2 is
completely filled up with the fuel 8 again when the fuel tank 2 is
replenished with the fuel 8 to immerse the guide pipe 4 and the
bracket 15 in the fuel 8.
Besides, a reflective surface 44 which reflects the ultrasonic wave
generated by the ultrasonic sensor 3, toward a liquid level 81, is
formed unitarily with the guide pipe 4 which defines the ultrasonic
transmission route between the ultrasonic sensor 3 and this
reflective surface 44. Accordingly, even in a case where the shape
of the fuel tank 2 is complicated, for example, where an extent
from the bottommost part of the fuel tank 2 to the highest liquid
level 82, namely, the liquid level 82 corresponding to the maximum
quantity of storage of the fuel 8 in the fuel tank 2 cannot be
perpendicularly seen through, the liquid level 81 in the fuel tank
2 can be reliably detected from the highest liquid level 82 to the
lowest liquid level by appropriately setting the position of the
reflective surface 44.
(Modification to Eleventh Embodiment)
As shown in FIG. 29, a modification to the fuel liquid level
detecting apparatus 1J of the eleventh embodiment is such that the
shape of the bracket 15 in the fuel liquid level detecting
apparatus 1J of the eleventh embodiment is partly altered. The
other constituents of the modification are constructed similarly to
the corresponding constituents of the fuel liquid level detecting
apparatus 1J of the eleventh embodiment, respectively.
In this modification, the bottom 15b of the bracket 15 is provided
with three protuberances 15f which protrude toward the ultrasonic
generation surface 31 of an ultrasonic sensor 3. The protuberances
15f are located at equiangular intervals, namely, at intervals of
120 degrees on a circumference which is concentric with the
ultrasonic generation surface 31.
When the ultrasonic sensor 3 is assembled to the bracket 15, the
ultrasonic generation surface 31 abuts against the three
protuberances 15f, and a gap whose length is substantially equal to
the height L of each protuberance 15f is defined between the
ultrasonic generation surface 31 of the ultrasonic sensor 3 and the
bottom 15b of the bracket 15 as shown in FIG. 29. The height L of
each protuberance 15f is set at a dimension at which the interspace
between the ultrasonic generation surface 31 and the bottom 15b is
sufficiently filled with a fuel 8 by a capillary action.
Accordingly, the interspace between the ultrasonic generation
surface 31 and the bottom 15b is sufficiently filled with the fuel
8, and the vibration energy of an ultrasonic wave generated from
the ultrasonic sensor 3 can be conveyed to the bracket 15 at a high
efficiency.
(Another Modification to Eleventh Embodiment)
As shown in FIG. 30, another modification to the fuel liquid level
detecting apparatus 1J of the eleventh embodiment is such that the
shape of the bracket 15 in the fuel liquid level detecting
apparatus 1J of the eleventh embodiment is partly altered. The
other constituents of the modification are constructed similarly to
the corresponding constituents of the fuel liquid level detecting
apparatus 1J of the eleventh embodiment, respectively.
In this modification, through holes 15c are respectively formed in
the upper and lower parts of the cylindrical wall of the bracket
15. Besides, the minimum distance F between a guide pipe 4 and the
outside surface of the cylindrical wall of the bracket 15 is set to
be greater than the diametric dimension d15c of each through hole
15c.
Accordingly, a fuel 8 which has entered the interspace between the
guide pipe 4 and the outer peripheral surface of the bracket 15
flows into the bracket 15 through the through holes 15c with ease,
and a gap G2 which is defined between the ultrasonic generation
surface 31 of an ultrasonic sensor 3 and the bottom 15b of the
bracket 15 is filled up with the fuel 8.
Also with this construction, the interspace between the ultrasonic
generation surface 31 and the bottom 15b is sufficiently filled
with the fuel 8, and the vibration energy of the ultrasonic sensor
3 can be conveyed to the bracket 15 at a high efficiency.
By the way, in each of the fuel liquid level detecting apparatus 1J
of the eleventh embodiment and the modifications thereof, the guide
pipe 4 is formed from an aluminum die casting alloy, while the
guide pipe 5 is formed of a stainless steel pipe. However, the
guide pipes 4 and 5 may well be formed from other substances.
Besides, in each of the fuel liquid level detecting apparatus 1J of
the eleventh embodiment and the modifications thereof, the guide
pipes 4 and 5 are formed as separate members, which are assembled
together, but they may well be unitarily formed as a single
member.
Besides, in each of the fuel liquid level detecting apparatus 1J of
the eleventh embodiment and the modifications thereof, the guide
pipe 5 may well be omitted.
Besides, in each of the fuel liquid level detecting apparatus 1J of
the eleventh embodiment and the modifications thereof, the
reflective surface 44 is shaped in a simple flat surface, but it
may well be shaped in a concave surface which is concave facing
both the ultrasonic generation surface 31 and the liquid level
81.
In each of the embodiments described above, the liquid level
detecting apparatus according to the invention has been exemplified
as being applied to the fuel liquid level detecting apparatus for
the automobile, but it may well be applied to others than the fuel
liquid level detecting apparatus. More specifically, the liquid
level detecting apparatus may well be applied to the liquid level
detection of any other liquid used in a vehicle, for example, an
engine oil, a brake fluid or a window washer liquid. Alternatively,
the liquid level detecting apparatus may well be applied for
detecting a liquid level in a liquid transporting tank which is
installed in a liquid transporting vehicle, for example, a tank
truck. Further, the liquid level detecting apparatus may well be
applied for detecting a liquid level in any of various containers
installed in others than the vehicle, or the liquid level of a
liquid flowing within any container.
* * * * *